Mines

The Mines are the second floor of the alternate path added in Repentance. This stage can be accessed by using 2 bombs to open the boarded up door that appears after defeating the boss of the Caves / Catacombs / Flooded Caves I or II, or Downpour / Dross II. The Mines has an underground theme consisting of mostly rock and fire themed enemies and obstacles. The alternative floor of the Mines is the Ashpit, unlocked after beating every single boss from the Mines.

The Mines are significantly more difficult than their standard counterparts, filled with stone and fire-themed enemies that boast greater health, aggression and occasionally resistances to damage. Most obstacles are rocks or spiked rocks, while Poops are almost non-existent. Tinted rocks have a high chance of spawning Tinted Rock Spiders. Travelling through it is only advised if you have already acquired Knife Piece 1 in Downpour and intend to access the Corpse, however, you will still be presented with an additional, blind option in the item rooms.

After defeating the Mines II's boss, a door leading to the next alternate chapter - Mausoleum - appears. It requires 2 full hearts to open. The damage taken ignores almost every form of damage reduction, including The Wafer and invincibility. Unlike other methods of health donation, red hearts will not be prioritized over more valuable hearts.

Unique Elements

Minecarts - Several rooms contain rail tracks with minecarts racing around on them, usually containing enemies or hazards. These enemies can be defeated as normal, and doing so will destroy the minecart.
Throwable Bombs - Bomb Grimaces can be commonly found in various rooms which infinitely produce red, throwable bombs. Walking into one will cause Isaac to pick it up, lighting the fuse, and giving a short time window to rid of the explosive by pressing any of the fire buttons.
Dark Rooms - Some rooms are very dark, having a more potent Curse of Darkness effect, leaving only a small aura of light around Isaac.

Monsters

Entity	ID	Description
Bony	227.0	Wanders around the room and throws a bone at Isaac when he is in sight.
Black Bony	277.0	Wanders around the room and throws three bones in a row at Isaac when he is in sight. Explodes upon death.
Fly Bomb	819.0	Flies toward Isaac, circling around him as it does. Turn into a tiny Bomb upon death.
Ink	61.3	Flies slowly towards Isaac. Fires four shots in the ordinal directions and leaves a puddle of slowing Black Creep upon death.
Bulb	61.5	Flies in erratic, angled movements toward Isaac if his active item has charges; on contact, they drain up to 2 charges, but never deal contact damage. If he has no active item, or no charges, they wander around the room aimlessly.
Danny	820.0	Walks toward Isaac and spits chaotic bursts of rocks at him, some of which may be Rock Spiders.
Coal Boy	820.1	Walks toward Isaac and spits hot coals at him, some of which may be Coal Spiders.
Blaster	821.0	Slowly wanders around and occasionally shoots Fly Bombs at Isaac.
Bouncer	822.0	Wanders around the room, avoiding Isaac. If Isaac stays close to one for long enough, it inflates and starts chasing him, gaining a chance to deflect shots and causing it to explode into lingering blood shots on death.
Dragon Fly	25.3.0	Flies across the room in straight diagonal lines, dealing contact damage. Upon death, creates four lines of fire in the cardinal directions; the fire nearly spans the length of an entire normal-sized room.
Dragon Fly X	25.3.1	Flies across the room in straight diagonal lines, dealing contact damage. Upon death, creates four lines of fire in the ordinal directions; the fire nearly spans the length of an entire normal-sized room.
Hard Host	27.3	Stationary enemy that is normally invulnerable. Raises its head up when Isaac gets close, revealing a fleshy stem that can be damaged. Shortly after raising its head, it slams its head down and fires a rock wave towards Isaac.
Quakey	823.0	Walks slowly toward Isaac, occasionally attempting to jump on Isaac, shooting out 8 rock shots when it hits the ground and causing rocks to fall from the ceiling.
Gyro	824.0	Rolls around like a wheel. Charges at Isaac when he is in line of sight, bouncing off of walls and obstacles as it does.
Grilled Gyro	824.1	Rolls around like a wheel. Charges at Isaac when he is in line of sight, bouncing off of walls and obstacles and creating fires behind itself as it does.
Fire Worm	825.0	Pops out of the ground in random locations in the lava and fires one flame at Isaac.
Dip	217.0	Slowly dashes in random directions, dealing contact damage.
Hardy	826.0	Dashes toward Isaac and deals contact damage creating rock projectiles when it hits a wall/obstacle. It spawns more rock projectiles the more times it crashes into obstacles, dying after doing so a third time.
Gurgle	87.0	Walks towards Isaac, dealing contact damage and periodically firing Ipecac shots at him; they are immune to this explosion, but other enemies are not. Can turn into a Splasher upon death.
Faceless	827.0	Wanders around the room, rarely firing a radial burst of six shots. Chases Isaac and fires shots more frequently after taking damage.
Mole	829.0	Burrows towards Isaac and jumps out the ground to fire 3 blood shots at him.
Rock Spider	818.0	Slowly crawls around the room. If it sees Isaac, it crawls at him, trying to deal contact damage. Turns into a Spider upon death. Turns into a Coal Spider if it touches fire.
Coal Spider	818.2	Quickly crawls around the room. If it sees Isaac, it crawls at him, trying to deal contact damage. Turns into a hot coal upon death that blocks shots and deals contact damage, but can be destroyed.
Migraine	869.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances. Releases multiple Troll Bombs upon death.
Splasher	238.0	Walks aimlessly around the room, firing Ipecac shots in random directions.
Blister	303.0	Slowly hops towards Isaac, occasionally spawning a Dark Ball. Spawns a Sack upon death.
Pon	840.0	Hops around the room, leaving damaging red creep wherever it lands. Upon death, its associated Brainless Knight dies with it.
Crispy	226.2	Slowly walks towards Isaac, but increases in speed as they take damage. Constantly passively takes damage.
Chubber	39.2	Randomly wanders around the room. Pauses to fire a Charger that deals one heart of damage when Isaac gets in its line of sight. The Charger is invulnerable, blocks Isaac's tears, has limited range, and flies back to the Chubber.
Soy Creep	240.1	Slowly crawls along walls to try to line up with Isaac and shoots a stream of shots seemingly affected by Soy Milk.
Wall Hugger	218.0	Moves around the room like Guts, damaging Isaac by contact. Cannot be destroyed.
Stone Grimace	42.0	Stationary and invulnerable monster that occasionally fires a blood shot at Isaac. Stops firing when room is cleared.
Vomit Grimace	42.1	Stationary and invulnerable monster that occasionally fires an Ipecac shot at Isaac. Stops firing when room is cleared.
Constant Stone Shooter	202.0	Stationary and invulnerable monster that continuously fires shots in a single direction.
Cross Stone Shooter	202.10	Stationary and invulnerable monster that continuously fires shots in four directions, alternating between cardinal and ordinal.
Bomb Grimace	809.0	Stationary and invulnerable monster that keeps a single Throwable Bomb spawned.
Quake Grimace	804.0	Stationary and invulnerable monster that jumps and fires a line of rocks in one direction upon landing.
Stoney	302.0	Chases Isaac and blocks tears, but does not deal contact damage. Temporarily pauses in exhaustion after a certain amount of time. Invulnerable; dies when the room is cleared.

Bosses


Reap Creep	Tuff Twins	Great Gideon	Hornfel

Knife Piece

If Isaac has Knife Piece 1, a special double-sized room will spawn in Mines II containing a minecart and a broken length of rail track leading to a boarded up door, resembling a Bedroom door. Behind this door lies the area in which Knife Piece 2 can be acquired. There are two methods for accessing this area:

Three Yellow Buttons can be found in rooms throughout the floor. One will be in the same room as the broken rail track, but the other two are randomly placed. Once all three buttons are pressed, the rail track will be repaired and once Isaac touches the minecart it will bring him into the special area.
If Isaac has flight and 2 Bombs, he can fly to boarded up door and blow it open. Other effects that open doors such as Dad's Key, Soul of Cain, Cracked Orb, etc. can also be used in place of bombs.

Upon entering this area, all passive items, active items, and trinkets will be rendered inactive, and Isaac's Bombs, coins, and Keys will be set to zero. Isaac will pass through several empty rooms before reaching a room with the Knife Piece 2. Once picked up, Mother's Shadow will spawn and chase Isaac until he reaches the entrance to the area and leaves. Once Isaac escapes, all his items will be reactivated, and Mother's Shadow will end her pursuit.

For more notes and details, see Mother's Shadow.

Unlockable achievements

Ashpit - Defeat all bosses in Mines.

Trivia

In Antibirth, the Mines used to have a different way of unlocking Knife Piece 2. Somewhere on the floor, there was a room containing four buttons. In the room, next to each button, were 1 to 4 small pebbles, indicating the order in which to press them. After all four buttons were pressed, the Knife Piece 2 would appear in the center of the room. This also wasn't the last knife piece, as there was a third piece to collect on the Mausoleum floor.
Moles will open their eyes if encountered in a dark room, however, this doesn't change their behavior.