Mega Satan
Mega Satan is the final boss in The Binding of Isaac: Rebirth.
Unlock
Mega Satan is located behind the Golden key door at the start of The Chest and the Dark Room. He is normally inaccessible.
To unlock Mega Satan, The Blue Baby (???) or The Lamb must have been defeated in an earlier run.
In subsequent runs, Angel Statues can be bombed to fight a Fallen Angel boss. When killed, they will drop one of two key pieces. Killing two Angel Statues, and thus collecting two key pieces, will form the fully completed key. This key is automatically used upon entering The Chest or the Dark Room on the Golden key door.
Alternatively, Dad's Key can be used to unlock the Golden Key Door instead of collecting the key pieces.
Passing through this Golden Key door and stepping onto the pentagram will initiate the Mega Satan fight. Good luck.
Attacks
- For the first part of the boss, you will have to shoot at his head, his hands will protect it from your attacks and respawn after a short while if "killed", you only need to defeat the head.
- After a certain threshold of damage, he will summon all four Horsemen of the Apocalypse by duo, Famine with Pestilence then Death with War. His face and hands will be unaccessible as he'll watch you fight, but once the four Horsemen are killed, they will return.
- After another threshold, he will summon all seven super sins, Super Envy first, followed by Super Lust with Super Wrath and finally Super Gluttony, Super Sloth, Super Greed and Super Pride together. You can use Super Gluttony's Brimstone to easily damage the others Sins.
- After a third threshold, he will summon a black version of the Angel boss found in the Angel Room. After it is killed, a stronger version of it will appear.
- After taking even more damage, Satan will sink into the darkness and rise up in his final phase as a skull.