Cain

Cain is a character unlocked by obtaining 55 or more coins at once in a run. He starts with two Red Heart containers, one Key, and Lucky Foot.

Cain also starts with Paper Clip after 68 coins have been donated to the Greed Donation Machine.

Lucky Foot now changes bad pills into good pills (similar to PHD, although not revealing their effect).

Notes

Cain's high starting luck, along with his Lucky Foot, will increase the chance of room drops and machines paying out. Luck-based tear effects are also made more effective.
- Lucky Foot makes pills a must-have by guaranteeing positive pill effects.
Unlocking Paper Clip is a priority, as Cain can spend those Keys elsewhere for greater rewards.
Cain is not a very good candidate for Devil Room deals early on, due to his low starting health.
- Angel Rooms are more valuable for Cain. As he is likely to have a large collection of coins or keys after a few floors, it is wise to open up Shops, bomb Shopkeepers, donate ten coins to a Donation Machine, or donate to a Beggar until he pays out to maximize the chances of an Angel Room.
Cain only being able to shoot tears from his right eye makes aiming easier, and lets him consistently peek around corners to shoot behind cover. This trait also affects certain items:
- The R U a Wizard? pill will cause Cain to only fire tears to his right.
- Blood Clot, Chemical Peel, and Stye have a 50% chance to do increased damage.
- Technology 2 will prevent him from firing normal tears, including tear-changing effects like Brimstone.
  - Technology 2 will no longer prevent him from firing normal tears and instead will cause him to also fire Technology lasers out of his right eye instead of his normal tears. These Technology shots have the same synergies and interactions with other items on top of the Technology 2 laser. Neptunus lets him fire tears normally. These lasers cannot be angled with momentum.

Item Interactions

Abel's tears become red and deal 7.5 damage when held by Cain.
Birthright: Grants +1 luck. All floors that can have special rooms contain an upgraded Arcade.
Technology 2: Effectively acts like the Technology item.
Eye Drops: Since his left eye is covered, it's simply a tears up instead of the normal effect of +40% fire rate on the left eye.

Unlockable Achievements

Cain's Other Eye - Complete the Boss Rush as Cain.

Glass Baby - Defeat Mom's Heart on Hard mode as Cain.

A Bag of Bombs - Defeat Satan as Cain.

A Bag of Pennies - Defeat Isaac as Cain.

Abel - Defeat The Lamb as Cain.

Cain's Eye - Defeat ??? as Cain.

Evil Eye - Defeat Ultra Greed as Cain.

Sack of Sacks - Defeat Ultra Greedier as Cain.

D12 - Defeat Hush as Cain.

Green Baby - Defeat Mega Satan as Cain.

Silver Dollar - Defeat Delirium as Cain.

Guppy's Eye - Defeat Mother as Cain.

A Pound of Flesh - Defeat The Beast as Cain.

The Hoarder - Use Red Key (etc.) to open the hidden closet in Home as Cain.

Picky Baby - Earn all Hard mode Completion Marks as Cain.

Unlockable Starting Items

Donate 68 Coins to the Greed Donation Machine - Start with Paper Clip

Gallery

Cain's transition screen portrait.
The spawn floor when playing Cain.
Cain's locked character icon.

Trivia

Cain appeared in the original Binding of Isaac, with the same unlock method.
Cain is a reference to the Biblical story of Cain and Abel, in which Cain commits the first murder by killing Abel.
- Abel also appears as an item in Rebirth.
- Cain's special interaction with Abel is also a reference to this.
Glass Baby could be a reference to Cain having a glass eye.
Cain's locked icon shows him bound in chains.
- He shares this trait with Magdalene, Samson, Eve, Lazarus, Bethany, and Jacob and Esau.
- He is the only character whose mouth is visible when locked.
The fact that he takes 55 coins to unlock may be a reference to how it is said that Jesus cast out 55 demons during his life.