| Defeat Satan for the 1st timeJudas|
Judas is a character unlocked after beating Satan for the first time. Judas starts with one red heart container, but has The Book of BelialUpon use increases damage by 2 for the current room and by a further +50% if the character also has the Blood of the Martyr.
Guarantees a Devil Room or Angel Room will be open after beating a boss while holding it, or increases the chance by 12.5%. upon starting, as well as 3 coins.
When a character dies after picking up the item Judas' ShadowAdds an extra life; upon death, it respawns Isaac as Black Judas with only two black hearts., they will respawn as Dark Judas. Dark Judas spawns with two black hearts, a damage multiplier of 2.00 (instead of Judas' 1.35 multiplier), and a base speed of 1.1. Similar to Azazel, Dark Judas can still gain heart containers despite starting with none. Dark Judas has the highest base damage multiplier of all the playable characters.
Dark Judas is considered by the game to be a separate character from Judas, but all of the Judas Completion Marks on Judas' post-it note can be completed with Dark Judas and unlockable items and/or achievements can be earned by completing objectives with Dark Judas.
- Judas has a great damage sustain during the run due to the The Book of BelialUpon use increases damage by 2 for the current room and by a further +50% if the character also has the Blood of the Martyr.
Guarantees a Devil Room or Angel Room will be open after beating a boss while holding it, or increases the chance by 12.5%.; try to keep the item until you have enough damage to grab another active item.
- The Book of Belial is also beneficial to hold on to, as it guarantees that the Devil Room or Angel Room will open after defeating a boss.
- The Book of Belial no longer guarantees a Devil Room or Angel Room, but still increases the chance to get one.
- Accept any health upgrade during the run, as Judas can be challenging without enough health. Grabbing items such as Bucket of LardGrants two empty heart containers and heals Isaac by half a heart, but decreases speed by 0.2. early in the game could be crucial for a good run.
- Dead CatSets the amount of red heart containers to 1, but gives Isaac 9 extra lives. After dying, Isaac is teleported to the last safe room. New heart containers can be obtained after picking up this item, but after each death, the number of heart containers is set to 1 again. can prove very useful if found early enough, since Judas starts with only one heart container. As well as granting 9 additional lives, it is also one of the Guppy items.
- ScapularOnce per room, when Isaac is reduced to his last half red Heart, the aura around his head temporarily vanishes and he is granted one Soul Heart. and other "low health activation" items are helpful for early floors, due to his low health.
- Blood of the MartyrIncreases Damage by 1, and turns Isaac's tears into blood tears.: Synergizes with Book of Belial for an extra 1.5x damage multiplier.
- Dead CatSets the amount of red heart containers to 1, but gives Isaac 9 extra lives. After dying, Isaac is teleported to the last safe room. New heart containers can be obtained after picking up this item, but after each death, the number of heart containers is set to 1 again.: Grants extra lives with no downsides as Judas only has one heart to start with.
- Whore of BabylonIncreases damage and speed whenever Isaac has half a red heart or less (one red heart for Eve), ignoring any soul or black hearts.: Due to his low health, Judas can easily take advantage of Whore of Babylon's effect.
- Judas is a reference to Judas Iscariot, the Twelfth Disciple. Judas betrayed Jesus to the Romans in exchange for thirty pieces of silver, represented by the three coins Judas starts the game with. Moreover, the coins are also believed to represent the three Abrahamic faiths, Judaism, Christianity, and Islam.
- Contrary to popular belief, Judas's fez is not a reference to the game Fez, created by Phil Fish. Edmund Mcmillen has stated that the initial statement was a joke and that he used the fez due to it being easily recognizable.
- Dark Judas is sometimes referred to as Black Judas.
- In the original Binding of Isaac, Judas was unlocked by beating The Womb for the first time. The character unlock was replaced with unlocking Eden in The Binding Of Isaac Rebirth.