Rotgut

Rotgut is one of the bosses that can appear in Corpse.

Behavior
In its first form, Rotgut spawns stationary in the middle of the room. It has a few attacks:
 * Protrudes a second mouth which spews brown shots, bones, Small Maggots, and Globin goo.
 * Fires bloody shots in all directions.

When the first form is reduced to 0 health, it will start sucking in everything in the room. Once Isaac is sucked in, he's dragged into a Crawlspace-like area to fight two more forms.

In its second form, Rotgut is stationary in the bottom right corner of the crawl space. It has several new attacks:
 * Shoots slow-moving curving bullets.
 * Shoots a chaotic burst of blood projectiles similar to Monstro throughout the lower half of the room while spitting small maggots.
 * Shoots a cluster of red bullets that fly in a wavelike pattern and fill up the bottom of the room.
 * Fires one large explosive bullet that releases regular bullets in random directions upon exploding.
 * Spews a burst of green projectiles along with a large poison cloud.
 * Fires a Brimstone laser that covers the lower half of the room.

After the second form is defeated, a passage will open up in the bottom right of the room, leading to the third form. In its third and final form, Rotgut is stationary and hangs from the ceiling, and has a few more attacks:
 * Fires pulsating bullets in 7 directions.
 * Causes bullets to fall from the top of the room. Once these bullets come in contact with a wall or floor, they split in two.
 * Spawns a series of 4-5 leeches from either the left or right side of the room at Isaac's height.
 * The last Leech has a chance to be an Adult Leech.

Once all three forms of Rotgut are defeated, Isaac is ejected out of the crawl space, returning to the boss room right before Rotgut dies properly.

Trivia

 * Rotgut's 1st form bears a strong resemblance with Nydus Worms from Starcraft II.
 * Rotgut's 2nd form seems to be a giant maggot that has infested the corpse to feed off of it.
 * This maggot has been nicknamed "Gus" by the developers.
 * Rotgut's 3rd form looks like a dead/rotten version of Mom's Heart, explaining Rotgut's name.
 * Rotgut is the name for grade of moonshine that is very poor quality, being poor enough to be deadly to drink. Isaac's mother was a known alcoholic, this could be the reason for rotgut's existence in her corpse.
 * Rotgut is the name of a Super Meat Boy level, one of Edmund McMillen's games.
 * Rotgut was significantly redesigned when it was ported into Repentance. Its first form was redesigned to a Fatty fused into the ground, while the third phase was changed to a non-specific organ. Only the maggot was unchanged.