Great Gideon

Great Gideon is a boss added in The Binding of Isaac: Repentance that can appear in the Mines and the Ashpit.

Behavior

Great Gideon is always fought in a vertical double-size room and has no health in a traditional sense. Instead, Isaac must battle 6 waves of monsters to beat him, similar to Greed Mode waves. Each wave begins once all enemies from the previous wave have been defeated.

He uses the following attacks during these waves:

Creates a vacuum that affects the whole room, pulling in Isaac and all monsters and monster projectiles. It also pulls in additional rock projectiles. Touching Gideon while he is performing this attack damages Isaac.
Spits 5 projectiles in a cone shape towards Isaac. The center projectile is larger and splits into 8 projectiles in a radial burst when it lands or hits something.
Charges up then spits large flame projectiles down the center of the arena that can occasionally leave small fires behind.
- Some enemies caught in this attack are turned into their flaming versions: Rock Spider into Coal Spider, Clotty into Grilled Clotty and Gyro into Grilled Gyro.
After the beginning of the 4th wave, Great Gideon charges up and releases a rock wave down the center of the room, breaking parts of the floor and leaving gaps.
- There is always at least 1 gap between the trail of holes created by this attack as to not completely trap Isaac on either end of the room.
Gideon does not spawn the next enemy wave during the middle of any of his attacks and only progresses a wave once he has finished.

After Isaac defeats all 6 waves of monsters, Great Gideon will deactivate, similar to a regular Stone Grimace.

Monsters

Mines Waves

Name	ID
Blaster	821.0
Bouncer	822.0
Clotty	15.0
Coal Boy	820.1
Coal Spider	818.2
Danny	820.0
Dragon Fly	25.3.0
Dragon Fly X	25.3.1
Faceless	827.0
Fire Worm	825.0
Fly Bomb	819.0
Gurgle	87.0
Gyro	824.0
Hardy	826.0
Ink	61.3
Quakey	823.0
Rock Spider	818.0
Soy Creep	240.1
Sucker	61.0
Walking Gut	88.1

Ashpit Waves

Name	ID
Big Bony	830.0
Blaster	821.0
Bone Fly	25.4
Bony	227.0
Carrion Princess	23.3
Coal Boy	820.1
Coal Spider	818.2
Crackle	87.1
Danny	820.0
Dragon Fly	25.3.0
Dragon Fly X	25.3.1
Dust	882.0
Flesh Maiden	880.0
Fly Bomb	819.0
Gurgle	87.0
Hard Host	27.3
Hardy	826.0
Migraine	869.0
Necro	828.0
Pasty	881.1
Rock Spider	818.0
Splasher	238.0

Gallery

Great Gideon in-game
Great Gideon summoning a wave.
Great Gideon about to perform his rock wave attack.
Great Gideon performing his fire attack.
Great Gideon performing his vacuum attack.
Great Gideon deactivated.
Great Gideon being defeated by Chaos Card.
Concept art for Great Gideon. (Referred to as "The Castle")

Notes

Great Gideon can be instantly killed with Chaos Card. Doing so reveals a unique 1x2 Crawl Space beneath him, containing two locked chests, two items and a key.
- This can be done at any time, even if he has already been defeated, as his deactivated body still remains after returning to the room.
- Defeating Great Gideon in this way plays a unique animation in which the Chaos Card gets lodged in his forehead before he explodes.
- Pressing on a Killswitch in the room similarly kills Great Gideon, and reveals the unique 1x2 Crawl Space. This also plays the unique animation of the Chaos Card in his head. Doing so is possible with D12
Completing waves will not charge active items.
Vanishing Twin will duplicate Great Gideon and increase the number of waves by 2. The waves themselves contain no extra enemies.
Great Gideon can be fought outside the Mines or the Ashpit via using a IV - The Emperor? card in {[s|Downpour}} or Dross. If encountered outside his regular stages, he has preset waves consisting of Frowning Gapers, Wall Creeps, Round Worms, Gurgles, and Suckers.

Trivia

He is the boss version of Stone Grimaces, resembling a giant version with his left eye replaced by 7 holes arranged in a hexagonal pattern, and his left backside appears rougher with several protruding rocks.
- When performing his rock wave attack, he grows spikes resembling a Quake Grimace's.
Great Gideon's name likely comes from Gideon, an Old Testament prophet and military leader known for winning a decisive battle against an overwhelming Midianite army with only an army of 300 Israelites — explaining the large amount of enemies the boss spawns.
The name Gideon is said to mean “hewer” which is an individual who works in a mine breaking stone.
Great Gideon is one of the few bosses with a unique health bar, aside from Dogma.
The Crawl Space that opens up when using Chaos Card on Gideon is titled "Gideon's Grave" in the game's code.
- According to developer NotYourSagittarius, this is a direct reference to Scott Pilgrim, a series of graphic novels.

Bugs

Bug!	Spawning Great Gideon with the debug console will spawn him with a normal boss healthbar instead of a "waves" mechanic. When Great Gideon attempts to spawn a wave of enemies, the game crashes.

Bug!	Dealing enough damage quickly enough (e.g. with Soy Milk) to the monsters Great Gideon creates can cause him to spawn the next wave before all enemies in the current one are dead.