Damage

Damage refers to the amount of damage each tear deals to enemies, and is represented by a sword. As damage increases, the size of the tears increases as well. However, tear size is not always a direct indication of how much damage tears will do; for example, items like Dead Onion and Tropicamide increase tear size without increasing damage. Tears will grow and shrink when damage changes, but tears of a certain size do not have a specific damage value, and two tears of the same size (in two different runs) are likely to have different damage values.

Effective Damage

The formula for damage is: $E f f e c t i v e D a m a g e = (C h a r B a s e D m g \times \sqrt{T o t a l D m g U p s \times 1.2 + 1} + F l a t D m g U p s) \times M u l t i p l i e r s$

where:

CharBaseDmg = The character's base damage multiplied by their multiplier,
TotalDmgUps = the total of all regular damage ups collected (not including special exceptions or damage multipliers),
FlatDmgUps = the total of all damage ups that are excluded from the above (for example, Curved Horn or Ipecac), and
EffectiveDmg = the approximate damage that can be expected per tear, or per 'tick' when using Brimstone or Technology 2.

This formula makes most damage upgrades less potent the more that Isaac has. For example, a Pentagram (+1 Damage) on Isaac would make his total damage 3.5 × (1 × 1.2 + 1)^0.5 = 3.5 × 1.48 = 5.19. Another Pentagram (+1+1) increases this to 6.45 (a 1.26 increase instead of a 1.69 increase). The higher a character's base damage, the more effective damage ups will be for that character. Flat damage modifiers and special adjustments like Polyphemus or Sacred Heart happen after the main formula.

Character Modifier

The character base damage is defined by a base number and a multiplier.

Eve^† and Tainted Magdalene: 0.75 × 3.50 = 2.625
Jacob^‡: 1.00 × 3.50 - 0.75 = 2.75
Isaac, Magdalene, Samson, Lazarus, Lilith, The Lost, Apollyon, The Soul, Bethany, Tainted Isaac, Tainted Judas, Tainted ???, Tainted Samson, Tainted Lazarus, Tainted Lilith, Tainted Keeper, Tainted Apollyon, Tainted Bethany, and Tainted Jacob: 1.00 × 3.50 = 3.50
Eden and Tainted Eden: 1.00 x 3.50 ± 1.0 = from 2.50 to 4.50
???: 1.05 × 3.50 = 3.675
Esau^‡: 1.00 × 3.50 + 0.25 = 3.75
Keeper, Cain, Tainted Cain, Tainted Eve, and Lazarus Risen: 1.20 × 3.50 = 4.20
Judas: 1.35 × 3.50 = 4.725
Azazel, The Forgotten, Tainted Azazel, Tainted Forgotten, and Dead Tainted Lazarus: 1.50 × 3.50 = 5.25
Lazarus Risen: 1.40 × 3.50 = 4.90 (+0.5 damage after each death, 6.20 effective damage on the first death)
Tainted Lost: 1.30 × 3.50 = 4.55
Black Judas: 2 × 3.50 = 7.00

^†: Whore of Babylon has the unique effect of increasing Eve's damage modifier from 0.75 to 1.00 when active. This does not apply to other characters, however.
^‡: Jacob and Esau have -0.75 and +0.25 flat damage, respectively: their base damage, as far as the damage formula is considered, is still 3.5 with a 1.0 multiplier.

Damage Multipliers

Some items multiply damage rather than simply adding to it. Damage multipliers (not to be confused with the aforementioned character-inherent base multiplier) do not simply multiply the character's damage once; the damage stat is constantly recalculated and the damage multipliers are multiplied with the end result. This means that if a character starts with 3.50 damage and gets a 2× multiplier, their effective damage will be 3.5×2 = 7.00. If an item that grants +1 damage is picked up, the character's effective damage will be 3.5×(1×1.2+1)^0.5×2 = 3.5×(2.2)^0.5×2 = 3.5×1.48×2 = 10.38, and not 7.00 + 1.

Most damage multipliers stack. For example, Proptosis and Eve's Mascara both provide a 2× multiplier; picking up both will give a total multiplier of 4×. The exception to this is the 1.5× damage multipliers provided by Cricket's Head, Magic Mushroom, and the combination of Blood of the Martyr and The Book of Belial. These multipliers do not stack; for example, picking up both Cricket's Head and Magic Mushroom will result in an overall 1.5× multiplier rather than the expected 2.25×. Some damage multipliers may be applied to certain flat damage increases, while others will not; see the section on the order in which damage multipliers and flat damage are applied for more information.

Reverse Formula

Consequently, the reverse formula to determine your damage bonuses from the displayed value is $B o n u s = \frac{1}{1.2} [{(\frac{E f f e c t i v e D a m a g e / M u l t i p l i e r s - F l a t D m g U p s}{C h a r B a s e D m g})}^{2} - 1]$ Multipliers is the product of all damage multipliers in effect.

Items that affect damage

Activated Items

Name	ID	Quote	Description	Quality
D100	5.100.283	REEROLLLLL!	Activates the combined effects of D4, The D6, and D20. Activates the combined effects of D1, D4, The D6, D7, D8, D10, D12, and D20.	3 1
Razor Blade	5.100.126	Feel my pain	Damages Isaac for one heart and grants +1.2 damage for the current room. Subsequent uses in the same room only take half a heart.	0
The Book of Belial	5.100.34	Temporary DMG up	+2 damage for the current room. Passively guarantees a Devil Room or Angel Room will appear while held. +2 damage for the current room. Passively increases the chance of finding a Devil Room or Angel Room while held.	2
The Nail	5.100.83	Temporary demon form	Gives one Soul Heart. For the current room; +0.7 damage, -0.18 speed, Isaac breaks rocks and deals contact damage. Gives half a Black Heart. For the current room; +2 damage, -0.18 speed, Isaac breaks rocks and deals contact damage.	2
D8	5.100.406	Reroll stats	Re-rolls Isaac's damage, tears, range, and speed.	2 1
Dataminer	5.100.481	109	Displaces enemy sprites for the current room and randomly increases one of Isaac's stats while decreasing another. Turns all items in the room into glitched items with random effects.	0
Potato Peeler	5.100.487	A pound of flesh	Removes a Heart Container, increases damage and range, and grants a Cube of Meat.	2
Void	5.100.477	Consume	Consumes all pedestal items in the room. Activated items will have their effects added to Void, and passive items will grant random stat upgrades.	4 3
Berserk!	5.100.704	Rip and tear	Isaac goes berserk for 5 seconds, greatly increasing his speed, tears, and damage, but restricting him to using a melee weapon instead of his tears. This item charges by dealing damage to enemies instead of clearing rooms.	2 1
Esau Jr.	5.100.703	Lost brother	Swaps between the current character and Esau Jr., who has +2 flat damage and flight. Characters have independent items and health. Dying as either character ends the run.	2 1
Golden Razor	5.100.555	Pain from gain	Spends 5 pennies to grant +1.2 damage for the current room. Grants 5 pennies when picked up for the first time.	1 0
Mega Mush	5.100.625	I'm a big boy now!	Gigantifies Isaac for 30 seconds, increasing damage and range while lowering tears, granting invulnerability, and allowing Isaac to crush enemies and obstacles he walks on. The effect persists between rooms.	4
Sulfur	5.100.556	Temporary demon form	Grants Brimstone for the current room.	3 2

Passive Items

Name	ID	Quote	Description	Quality
20/20	5.100.245	Double shot	Isaac fires two tears at once, one from each eye. 0.8× damage multiplier.	4
A Lump of Coal	5.100.132	My Xmas present	The more distance tears travel, the more damage they will do.	3
Abaddon	5.100.230	Evil + DMG up + fear shot	+1.5 damage, +0.2 speed. Removes all Red Heart containers, grants six Black Hearts, and adds a chance to shoot fear tears. +1.5 damage, +0.2 speed. Grants two Black Hearts, converts all Red Heart Containers into Black Hearts, and adds a chance to shoot fear tears.	3
Blood Clot	5.100.254	DMG + range up	Tears fired from the left eye have +1 flat damage, +5 range, and +0.5 tear falling speed. Tears fired from the left eye have +1 flat damage and +2.75 range.	2
Blood of the Martyr	5.100.7	DMG up	+1 damage. Isaac shoots blood tears.	3
Bloody Lust	5.100.157	RAGE!	Increases Isaac's damage whenever he takes damage, up to six times. The bonus resets when entering a new floor.	2
Brimstone	5.100.118	Blood laser barrage	Tears are replaced with a blood laser beam that pierces through all enemies and obstacles in its path and deals high damage. Can only be fired after a short charge-up period.	4
Capricorn	5.100.307	All stats up	Adds 1 Red Heart container, gives +0.5 Damage, +0.1 Speed, +1.5 Range, and -1.0 Tear Delay, and gives 1 Bomb, Penny, and Key. Adds 1 Red Heart container, gives +0.5 Damage, +0.1 Speed, +0.75 Range, and +0.5 Fire Rate, and gives 1 Bomb, Penny, and Key.	3
Cat-o-nine-tails	5.100.165	Shot speed + damage up	+1 damage, +0.23 shot speed.	3
Ceremonial Robes	5.100.216	DMG + evil up	Grants 3 Black Hearts and +1 damage.	3
Champion Belt	5.100.208	DMG + challenge up	+1 damage. Increases the chance of champion enemies appearing by 15%.	3
Charm of the Vampire	5.100.62	DMG up + kills heal	Heals Isaac for a Half Red Heart for every 13 enemies killed. +0.3 damage.	1 2
Chemical Peel	5.100.154	DMG up	Tears fired from the left eye have +2 flat damage.	2
Cricket's Head	5.100.4	DMG up	Increases Damage by 0.5, and increases damage multiplier by ×1.5.	4
Dark Matter	5.100.259	DMG up + fear shot	+1 damage, adds a chance to shoot fear tears.	3
Death's Touch	5.100.237	Piercing shots + DMG up	+1.5 damage, -0.3 tears. Tears are replaced with large piercing scythes.	3
Eve's Mascara	5.100.310	DMG up, tears + shot speed down	Doubles damage, halves tears stat, and greatly reduces shot speed. Doubles damage, 0.66x tears multiplier, and greatly reduces shot speed.	3
Experimental Treatment	5.100.240	Some stats up, some stats down	Randomly increases and decreases some of Isaac's stats. Increases four random stats and decreases the other two.	1
Godhead	5.100.331	God tears	Grants homing tears with a damaging halo. +0.5 Damage, -0.3 Tears -0.3 Shot Speed, +0.8 Tear Falling Speed, and +1.2 Range. Grants homing tears with a damaging halo. +0.5 Damage, -0.3 Tears, and -0.3 Shot Speed.	4
Growth Hormones	5.100.70	Speed + DMG up	+1 damage, +0.4 speed. +1 damage, +0.2 speed.	3
Guillotine	5.100.206	DMG + tears up. An out-of-body experience!	Isaac's head becomes an orbital familiar that blocks shots and deals contact damage. Tears are still fired from the rotating head. +1 damage, -1 tear delay. +1 damage, +0.5 fire rate.	2 0
Ipecac	5.100.149	Explosive shots	Replaces tears with explosive and poisoning projectiles fired in an arc from the mouth.	4
Iron Bar	5.100.201	DMG up + concussive tears	+0.3 damage. Adds a chance to shoot concussive tears, causing enemies to walk around randomly.	2
Jesus Juice	5.100.197	Damage + range up	+0.5 damage, +0.25 range, +0.5 tear falling speed. +0.5 damage, +1.5 range.	2
Libra	5.100.304	You feel balanced	Gives 6 Coins, 6 Bombs, and 6 Keys and balances out all attributes.	1
Magic Mushroom	5.100.12	All stats up!	Makes Isaac bigger. Adds one Red Heart Container, +0.3 Damage, x1.5 damage multiplier, +5.25 Range, +0.3 Speed, and restores all Health. Makes Isaac bigger. Adds one Red Heart Container, +0.3 Damage, x1.5 damage multiplier, +2.5 Range, +0.3 Speed, and restores all Health.	4
MEAT!	5.100.193	DMG + HP up	Grants one full Red Heart container, +0.3 damage. Heals 1 additional Red Heart	2
Missing No.	5.100.258	Syntax error	Randomizes all passive items and stats upon pickup and at the start of each succeeding floor.	0
My Reflection	5.100.5	Boomerang tears + DMG up + luck down	Gives Isaac's tears a boomerang effect. +1.5 range, +1 tear falling speed, x1.6 shot speed multiplier. 2x + 1.5 range, +1.5 damage, -1 luck, 1.6x shot speed multiplier.	2 3
Odd Mushroom	5.100.120	Tears + speed up, DMG down	+1.7 tears, +0.3 speed, slightly reduces damage.	2
Odd Mushroom	5.100.121	HP + DMG up, speed down	Grants one empty Heart container, +0.3 damage, +0.25 range, +0.5 tear falling speed, and -0.1 speed. Grants one full Heart container, +1 damage, +1.5 range, and -0.2 speed	2
Pentagram	5.100.51	DMG up	+1 damage, increases Devil Room / Angel Room chance by 10%.	3
Polyphemus	5.100.169	Mega tears	Isaac fires huge tears that deal massive damage, but fire rate is greatly decreased. If a tear kills an enemy, it travels on with any leftover damage.	4
Proptosis	5.100.261	Short range mega tears	Tears start out massive with high damage, and then shrink down and become weaker over a short range.	3
Sacred Heart	5.100.182	Homing shots + DMG up	Adds a Red Heart Container. Grants homing tears, a x2.3 Damage multiplier, +1 flat Damage, -0.4 Tears, -0.25 Shot Speed, and +4.125 Range. Adds a Red Heart Container. Grants homing tears, a x2.3 Damage multiplier, +1 flat Damage, -0.4 Tears, and -0.25 Shot Speed.	4
SMB Super Fan	5.100.189	All stats up	+1 Red Heart container, +0.3 damage, +0.2 tears, +0.2 speed, +0.5 range, +1 tear falling speed. Fully restores all red hearts. +1 Red Heart container, +0.3 damage, +0.2 tears, +0.2 speed, +2.5 range. Fully restores all red hearts.	3
Soy Milk	5.100.330	DMG down + tears way up	Tears are smaller and do much less damage, but fire in very rapid succession.	2
Steven	5.100.50	DMG up	+1 damage.	3
Stigmata	5.100.138	DMG + HP up	+0.3 damage, grants one full Red Heart container. Heals 1 additional Red Heart.	2
Synthoil	5.100.345	DMG + range up	+1 damage, +5.25 range, +0.5 tear falling speed. +1 damage, +2.5 range.	3
The Halo	5.100.101	All stats up	Grants one full Red Heart container, +0.3 damage, +0.2 tears, +0.25 range, +0.3 speed, and +0.5 tear falling speed. Grants one full Red Heart container, +0.3 damage, +0.2 tears, +1.5 range, and +0.3 speed. Heals 1 additional Red Heart.	2 3
The Mark	5.100.79	DMG + speed up	Grants one Soul Heart, +1 damage, and +0.2 speed. Grants one Black Heart, +1 damage, and +0.2 speed.	3
The Negative	5.100.328	Fate chosen	If Isaac has half a red heart or no red hearts after taking damage, all enemies in the room take significant damage. Allows entrance into the Dark Room. +1 Damage and also allows access to Home.	2
The Pact	5.100.80	DMG + tears up	Grants two Soul Hearts, +0.5 damage, and +0.7 tears. Grants two Black Hearts, +0.5 damage, and +0.7 tears.	3
The Peeper	5.100.155	Plop!	Spawns a familiar that slowly floats around the room in a zig-zag pattern, damaging enemies it passes through. Increases the damage of tears from Isaac's left eye by 35%.	2
The Small Rock	5.100.90	DMG up + speed down	+1 damage, +0.2 tears, -0.2 speed.	3
Whore of Babylon	5.100.122	Curse up	Grants +1.5 Damage and +0.3 Speed whenever Isaac has a Half Red Heart or less.	2
8 Inch Nails	5.100.359	Stick it to 'em!	+1.5 damage. Replaces Isaac's tears with nails, which have increased knockback.	3
Crown Of Light	5.100.415	The untainted gain power	+2 Soul Hearts. While Isaac has no empty red hearts, grants 2x damage, -0.3 shot speed, and increased range. Regardless of health, the crown deactivates for the current room when Isaac takes damage.	4
Dead Eye	5.100.373	Accuracy brings power!	Isaac's damage increases each time an enemy is hit. Damage is reset upon missing a shot.	3
Lusty Blood	5.100.411	Their blood brings rage!	Isaac's damage increases for the current room each time he kills an enemy.	3
Maw Of The Void	5.100.399	Consume thy enemy!	Isaac can charge and unleash a black ring that rapidly deals damage around him. The ring can cause enemies to drop Black Hearts. +1 damage.	3
Purity	5.100.407	Aura stat boost	Boosts one of Isaac's stats depending on the color of the aura around him. The aura disappears upon taking damage and reappears with a random color upon entering a new room. Red boosts damage, blue boosts tears, yellow boosts speed, and orange boosts range.	3
Succubus	5.100.417	Damage booster	Spawns a flying familiar that bounces around the room with a black aura, dealing rapid damage to any enemies inside it. While standing in the aura, Isaac gains a 1.5× tear damage multiplier.	3
Zodiac	5.100.392	The heavens will change you	Gives Isaac a random zodiac item effect that changes every floor.	1
Adrenaline	5.100.493	Panic = power	Increases damage based on how many empty Red Heart containers Isaac has.	2 1
Bozo	5.100.513	Party time!	+0.1 flat damage, grants a Soul Heart. Enemies can randomly become briefly charmed or feared. Taking damage has a chance to spawn a Rainbow Poop.	2
Camo Undies	5.100.497	Camo kid	Isaac becomes camouflaged at the beginning of each room. Until he shoots, all non-boss enemies will be confused. Isaac gains +0.5 Speed while camouflaged, and gains Tears and Damage upon breaking it.	3
Death's List	5.100.530	Just hope you're not next...	Grants a pickup or stat upgrade if all enemies in a room are killed in the order they are marked.	2 1
Dog Tooth	5.100.445	Bark at the moon!	+0.3 damage, +0.1 speed. Plays a howl or bark sound when entering a room with undiscovered Secret Rooms or Crawl Spaces.	2
Haemolacria	5.100.531	I'm seeing red...	Turns Isaac's tears into large blood tears fired in an arc. Upon hitting the floor, an obstacle, or an enemy, they burst into many smaller tears in all directions. Increases tear delay.	4
Hallowed Ground	5.100.543	Portable sanctuary	Spawns a white poop familiar, which turns into a White Poop when Isaac is hurt. White poop has an aura that increases tear fire rate and can block enemy shots. The aura also increases damage by 20% and gives homing.	1
Sulfuric Acid	5.100.463	Acid tears!	+0.3 damage. Adds a chance to fire acidic tears which can destroy obstacles and open doors.	2
Almond Milk	5.100.561	DMG down + tears up + you feel nutty	Quadruples fire rate, with ×0.3 damage multiplier. Each tear is given a random effect that alters its movement.	1
Binge Eater	5.100.664	All you can eat	+1 Red Heart Container and fully heals Isaac. Item pedestals also offer a random food item. Picking up a food item temporarily grants +3.6 damage and permanently boosts 2 stats.	4
Blood Oath	5.100.569	Bleed me dry	Stabs Isaac at the beginning of each floor, draining his Red Hearts. Increases damage and speed for the floor based on the amount drained.	1
Candy Heart	5.100.671	Power of love	Gives Isaac a permanent stat boost whenever he heals with Red Heart pickups.	1
Consolation Prize	5.100.644	+1 to lowest stat	Increases Isaac's lowest stat and drops either 3 Coins, 1 Bomb, or 1 Key depending on what Isaac has the least of.	1
Dogma	5.100.633	Ascended	Grants flight, +2 damage, and increases speed to 1.1. Grants enough health to have 6 full hearts, if possible. Grants the Holy Mantle effect for the room it was obtained in. Automatically given to Isaac after defeating Dogma.	3
Eye of the Occult	5.100.572	DMG up + range up + controlled tears	+1 damage, +2 range, -0.16 shot speed. Isaac's tears can be controlled mid-flight with tear controls.	3
False PHD	5.100.654	Worse pills + evil up	Converts good pills into bad pills and identifies all pills. Bad pills now have secondary positive effects. Grants one Black Heart.	2
Glass Eye	5.100.730	DMG + luck up	+0.75 damage, +1 luck.	3
Heartbreak	5.100.694	Eternal sorrow	Grants 3 broken hearts and +0.25 damage for every broken heart Isaac has. Every otherwise fatal hit will add 2 more until Isaac has nothing but broken hearts.	3
Immaculate Heart	5.100.573	Halo of tears	Adds one Red Heart Container and fully restores health. x1.2 damage multiplier. Isaac will occasionally fire extra tears that orbit around him.	3
Keeper's Sack	5.100.716	Spending power	Gives range, speed, or damage when buying things from a shop. Spawns three coins and a Key on pickup.	3
Mom's Ring	5.100.732	DMG up	+1 Damage. Drops a random Rune or Soul Stone upon pickup.	3
Red Stew	5.100.621	Full HP + temporary DMG up	Refills all heart containers. Grants an enormous damage boost that wears off over time.	2
Redemption	5.100.673	Deliver me from evil	If Isaac enters a Devil Room but leaves without taking/opening anything in it, he gets +1 Damage and a Soul Heart at the start of the next floor.	2
Sanguine Bond	5.100.692	He awaits your offering	Spawns a special set of spikes in the Devil Room. Taking damage from the spikes has a chance to grant a reward.	1
Sausage	5.100.669	All stats up	Adds a Red Heart Container, fully heals Isaac, and gives +0.2 Speed, +0.5 Damage, +0.5 Tears, +2.5 Range, +0.2 Shot Speed, and +1.0 Luck. Increases the chance of encountering a Devil Room, Angel Room, and/or Planetarium each by 6.9%.	3
Sol	5.100.588	Radiant victory	Reveals the location of the Boss Room. Upon defeating a boss, activates XIX - The Sun, fully recharges Isaac's active item, grants bonus damage and luck for the rest of the floor, and removes curses.	2
Soul Locket	5.100.686	Power of faith	Gives Isaac a permanent stat boost whenever he picks up a Soul Heart.	1
Stapler	5.100.708	DMG up	+1 Damage. Prevents Isaac from firing tears from his left eye, like Cain.	3
Star of Bethlehem	5.100.651	Follow the light	Spawns a star familiar that slowly travels towards the Boss Room, giving an aura that increases damage and tears and grants homing tears.	3
Stye	5.100.731	DMG + range up	Tears fired from Isaac's right eye have +28% Damage, +6.5 Range, and -0.3 Shot Speed.	2
Terra	5.100.592	Born to rock	+1 Damage. Replaces tears with rocks that deal variable damage, have increased knockback, and can destroy obstacles.	3
Technology 2	5.100.152	Extra laser	Replaces the tears fired from Isaac's right eye with a rapid-firing low damage piercing laser. Damage down.

Trinkets

Name	ID	Quote	Description
Curved Horn	5.350.35	DMG up	+2 flat damage.
Liberty Cap	5.350.32	Touch Fuzzy, Get Dizzy	Adds a chance when entering a room to gain Mini Mush, Odd Mushroom, Odd Mushroom, or The Compass for one room. Adds a chance when entering a room to gain a random passive mushroom item for one room.
Red Patch	5.350.40	Your rage grows	Grants a chance to gain +1.8 damage for the current room upon taking damage.
Samson's Lock	5.350.58	Your rage grows	1/15 chance to gain +0.5 damage for the current room each time an enemy dies.
Black Feather	5.350.80	With darkness comes power	Increases Isaac's Damage for each 'evil' item or trinket he possesses.
Cracked Dice	5.350.67	You feel cursed... kinda.	Activates Has a chance to activate the effect of The D6, D8, D10, D12, or D20 (chosen randomly) whenever Isaac takes damage.
Cracked Crown	5.350.92	Stat booster	Decreases Isaac's tear delay by 20%, and improves the effectiveness of his other stat upgrades by 33%. Improves the effectiveness of stat upgrades by 20%.
Dim Bulb	5.350.101	I think it's broken	Provides a boost to all stats when Isaac's active item is completely uncharged.
Vibrant Bulb	5.350.100	It needs power	Provides a boost to all stats when Isaac's active item is fully charged.
Azazel's Stump	5.350.162	Unleash your inner demon	When clearing a room, adds a 33% chance to turn into Azazel until clearing another.
Broken Syringe	5.350.132	Mystery medicine	Grants a chance to gain a random syringe effect for the current room.

Cards and Runes

Name	ID	Message	Description
III - The Empress	5.300.4	May your rage bring power	Triggers the Whore of Babylon effect (+1.5 Damage, +0.3 Speed) for the current room, regardless of Isaac's total health.
XI - Strength	5.300.12	May your power bring rage	Grants the effects of Magic Mushroom (minus the health restoration) for one room. The added Red Heart container is not removed if doing so would kill Isaac.
XV - The Devil	5.300.16	Revel in the power of darkness	Triggers The Book of Belial effect, granting +2 Damage for the current room.
Black Rune	5.300.41	Void	Deals 40 damage to all enemies in the room. Consumes all pickups in the room and turns them into Blue Flies and Spiders. Consumes all pedestal items in the room and turns them into random stat upgrades.
Huge Growth	5.300.52	Become immense!	For the current room, makes Isaac larger, allows him to crush obstacles he walks on, and grants +7 flat Damage and +30 Range. For the current room, makes Isaac larger, allows him to crush obstacles he walks on, and grants +7 flat Damage and +3 Range.
XIX - The Sun?	5.300.75	May the darkness swallow all around you	Gain Spirit of the Night and +1.5 Damage for the current floor. Turns Isaac's Red Heart Containers into Bone Hearts, but they revert once the effect ends. Also causes Curse of Darkness that cannot be dispelled.
Soul of Judas	5.300.84	Right behind you	Increases Isaac's speed and makes him invulnerable for 3 seconds and allows him to pass through enemies. Damages all enemies and destroys all projectiles Isaac ran through when the effect ends, and grants a temporary Damage bonus for each enemy and projectile hit.
Soul of Samson	5.300.87	Slay a thousand	Isaac turns berserk for 10 seconds, replacing his tears with a melee jawbone club and gaining +0.4 Speed, some Tears, and +3 flat Damage.

Items that multiply damage

Positive Multiplier

Name	ID	Quote	Description	Quality
Cricket's Head	5.100.4	DMG up	Increases Damage by 0.5, and increases damage multiplier by ×1.5.	4
Eve's Mascara	5.100.310	DMG up, tears + shot speed down	Doubles damage, halves tears stat, and greatly reduces shot speed. Doubles damage, 0.66x tears multiplier, and greatly reduces shot speed.	3
Magic Mushroom	5.100.12	All stats up!	Makes Isaac bigger. Adds one Red Heart Container, +0.3 Damage, x1.5 damage multiplier, +5.25 Range, +0.3 Speed, and restores all Health. Makes Isaac bigger. Adds one Red Heart Container, +0.3 Damage, x1.5 damage multiplier, +2.5 Range, +0.3 Speed, and restores all Health.	4
Polyphemus	5.100.169	Mega tears	Isaac fires huge tears that deal massive damage, but fire rate is greatly decreased. If a tear kills an enemy, it travels on with any leftover damage.	4
Sacred Heart	5.100.182	Homing shots + DMG up	Adds a Red Heart Container. Grants homing tears, a x2.3 Damage multiplier, +1 flat Damage, -0.4 Tears, -0.25 Shot Speed, and +4.125 Range. Adds a Red Heart Container. Grants homing tears, a x2.3 Damage multiplier, +1 flat Damage, -0.4 Tears, and -0.25 Shot Speed.	4
Crown Of Light	5.100.415	The untainted gain power	+2 Soul Hearts. While Isaac has no empty red hearts, grants 2x damage, -0.3 shot speed, and increased range. Regardless of health, the crown deactivates for the current room when Isaac takes damage.	4
Dead Eye	5.100.373	Accuracy brings power!	Isaac's damage increases each time an enemy is hit. Damage is reset upon missing a shot.	3
Succubus	5.100.417	Damage booster	Spawns a flying familiar that bounces around the room with a black aura, dealing rapid damage to any enemies inside it. While standing in the aura, Isaac gains a 1.5× tear damage multiplier.	3
Haemolacria	5.100.531	I'm seeing red...	Turns Isaac's tears into large blood tears fired in an arc. Upon hitting the floor, an obstacle, or an enemy, they burst into many smaller tears in all directions. Increases tear delay.	4
Hallowed Ground	5.100.543	Portable sanctuary	Spawns a white poop familiar, which turns into a White Poop when Isaac is hurt. White poop has an aura that increases tear fire rate and can block enemy shots. The aura also increases damage by 20% and gives homing.	1
Immaculate Heart	5.100.573	Halo of tears	Adds one Red Heart Container and fully restores health. x1.2 damage multiplier. Isaac will occasionally fire extra tears that orbit around him.	3
Star of Bethlehem	5.100.651	Follow the light	Spawns a star familiar that slowly travels towards the Boss Room, giving an aura that increases damage and tears and grants homing tears.	3

Character-specific damage multipliers:

Eve + Whore of Babylon - Raises her damage multiplier from 0.75× to 1× while the whore effect is active. (It does not have this effect for any other character.)
Judas + The Book of Belial + Birthright + Damocles - 1.4× damage multiplier while the Damocles effect is active.
Dying with Judas' Shadow transforms the player into Black Judas, who has a 2× damage multiplier, which is the highest character-based damage multiplier in the game.

Synergy-specific damage multipliers:

The Book of Belial + Blood of the Martyr - 1.5× damage multiplier. (The multiplier is shared with Cricket's Head and Magic Mushroom.)
Brimstone + Brimstone - 1.2× damage multiplier.
Brimstone + Technology - 1.5× damage multiplier.

Random Multiplier

Name	ID	Icon	Quote	Description	Quality
D100	5.100.283		REEROLLLLL!	Activates the combined effects of D4, The D6, and D20. Activates the combined effects of D1, D4, The D6, D7, D8, D10, D12, and D20.	3 1
D8	5.100.406		Reroll stats	Re-rolls Isaac's damage, tears, range, and speed.	2 1

Negative Multiplier

Name	ID	Quote	Description	Quality
20/20	5.100.245	Double shot	Isaac fires two tears at once, one from each eye. 0.8× damage multiplier.	4
Odd Mushroom	5.100.120	Tears + speed up, DMG down	+1.7 tears, +0.3 speed, slightly reduces damage.	2
Soy Milk	5.100.330	DMG down + tears way up	Tears are smaller and do much less damage, but fire in very rapid succession.	2
Almond Milk	5.100.561	DMG down + tears up + you feel nutty	Quadruples fire rate, with ×0.3 damage multiplier. Each tear is given a random effect that alters its movement.	1
Technology 2	5.100.152	Extra laser	Replaces the tears fired from Isaac's right eye with a rapid-firing low damage piercing laser. Damage down.

Note that Odd Mushroom is not a "real" damage multiplier in that it only affects the increases from other items. For example, if you only had Eve's Mascara for a 2× damage multiplier and nothing else, then Odd Mushroom would only grant a flat -0.4 damage (because nothing would be multiplied by 0.9).

The order that damage multipliers and flat damage are applied

Order	Item	Damage	Notes
0	Any normal damage up not listed below
1	Odd Mushroom	TotalDmgUps * 0.9	The normal damage ups below this don't get this multiplier
2	Odd Mushroom	-0.4
	Black Feather	+0.5 per evil item
	Camo Undies	+10.5	Fades quickly over time
	Dark Arts	+1 per enemy/bullet	Fades over time
	Golden Razor	+1.2
	Lazarus Risen	+0.5	Permanent damage up from reviving
	Lusty Blood	+0.5 per enemy, up to 5 max	Both items share the same max
	Samson's Lock	+0.5 per enemy, up to 5 max	Both items share the same max
	The Nail	+2
	Purity	+4	With damage aura
	Razor Blade	+1.2
	Red Patch	+1.8
3	Polyphemus	flat +4	These don't stack with each other
3	Polyphemus + 20/20/The Inner Eye/Mutant Spider	flat +5	These don't stack with each other
4	Polyphemus	×2	This doesn't apply with 20/20/The Inner Eye/Mutant Spider
4	Character multiplier	See above section
5	Character flat damage	See above section
5	Esau Jr.	flat +2
6	Mega Mush	×4
7	Berserk!	flat +3
	Bozo	flat +0.1
	Candy Heart	flat +0.1
	Consolation Prize	flat +1
	Curved Horn	flat +2
	Dataminer	flat +1 or -1
	Death's List	flat +1
	Experimental Treatment	flat +1 or -1
	The Forgotten + Mom's Knife	flat +4
	Huge Growth	flat +7
	Missing No.	flat +1 or -1
	Potato Peeler	flat +0.2
	Soul Locket	flat +0.2
	Void	flat +1
8	Brimstone + Brimstone	×1.2	Doesn't apply to Haemolacria and overrides Brimstone + Technology
	Crown Of Light	×2
	Sacred Heart	×2.3
9	Sacred Heart	flat +1
10	Judas + Birthright + Damocles	×1.4
11	Judas + Birthright + Damocles	flat +1	This effect grants two separate damage boosts, with the order of application excluding the flat damage boost from the multiplier.
12	Hallowed Ground	×1.2	These don't stack with each other
	Immaculate Heart
	Star of Bethlehem
13	Adrenaline	flat ((2 × MissingHearts) ^ 1.6) × 0.1
13	Bloody Lust	flat +6 max
14	Azazel + The Ludovico Technique	×0.5
	Brimstone + Technology	×1.5	These don't stack with each other
	Haemolacria	×1.5	These don't stack with each other
15	Ipecac	flat +40	These don't stack with each other
15	Ipecac + Brimstone / Dr. Fetus / The Forgotten / The Ludovico Technique / Mom's Knife / Tech X / Technology	flat +2	These don't stack with each other
16	20/20	x0.8
	Almond Milk	x0.3
	Cricket's Head	×1.5	These don't stack with each other
	Magic Mushroom
	The Book of Belial + Blood of the Martyr
	D8	×0.5 to ×2.0
	Dead Eye	×2 max
	Eve's Mascara	×2
	Soy Milk	×0.2	Overridden by Almond Milk
	Star of Bethlehem	×1.5	While the total damage boost from Star of Bethlehem amounts to ×1.8, splitting it into two portions causes it to interact in unusual ways with other damage boosts. See the item's page for details.
	Succubus	×1.5
17	Cracked Crown	×1.2 for damage over 3.5
17	Tainted Bethany's stat multiplier	x0.75 for damage over 3.5

Other

The Spun transformation increases damage by 2.
The Conjoined transformation decreases damage by 0.3.
In co-op, Rage Baby, Revenge Baby, and Belial Baby will occasionally briefly increase damage. Dark Baby will occasionally briefly increase all stats, including damage. Buddy Baby will occasionally briefly grant the Guillotine effect, which increases damage. Whore Baby will occasionally briefly grant the Whore of Babylon effect, which increases damage.
The horse Power Pill! activates the Huge Growth effect for the current room, which grants +7 flat damage.
Standing next to a White Poop or a white dip grants a x1.2 damage multiplier.
Standing on a brown creep produced by Tainted ??? or IBS grants +1 damage.
Lazarus Risen + Birthright: Grants +7.2 damage which fades away quickly.

The Binding of Isaac: Rebirth

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