Mega Satan is an unlockable boss in The Binding of Isaac: Rebirth. He is the final boss of Ending 16.

Mega Satan is located behind the golden gate at the starting room of The Chest and the Dark Room. To unlock Mega Satan, the following criteria must be fulfilled:

Collecting both key pieces will form the fully completed key, which is automatically used upon entering The Chest or the Dark Room on the golden gate. Alternatively, Dad's Key can be used to unlock the Golden Key Door instead of the key pieces. Dad's Key is unlocked by collecting both key pieces in an earlier run. Get out of Jail Free Card can also unlock the Golden Key Door if used in the starting room of The Chest or the Dark Room. Mr. ME! can also unlock the door if the item is aimed at it.



Stepping on spikes in a Sacrifice Room for the 9th and 11th times spawn Uriel and Gabriel, who will drop their respective key pieces. Stepping on spikes for the 12th time and beyond has a 50% chance to teleport Isaac to the Dark Room, where the door will be unlocked if both key pieces were picked up.

Passing through this Golden Key door and stepping onto the pentagram will initiate the Mega Satan fight.

After taking even more damage, Mega Satan will sink into the darkness and rise in his final phase as a skull. His final form does not spawn any other enemies; instead, he fires complex, bullet hell-style shots. Possible patterns include:

Streams of red shots

Rings and streams of multi-colored fire

Streams of simultaneous red and black shots, which move in different patterns

The same brown shot attack from the first phase.

Rings of black shots that pulse outwards

Streams of black shots that move outwards in a Ring Worm pattern

Streams of metallic gray shots which move outwards in a zigzag pattern

Rings of metallic gray shots that move in a Wiggle Worm pattern

As Mega Satan takes damage during this phase, his skull will begin to crack. After this final phase is defeated, the game ends and Ending 16 plays.

If The Void is unlocked, there is a 50% chance that the game will not immediately end, and Mega Satan will instead drop an ending chest along with a portal. Entering the chest ends the game and plays the cutscene while entering the portal will take Isaac to The Void.

Mega Satan in-game.

Mega Satan's final form in-game.

Mega Satan as one of Delirium's forms.

??? ahead of the Golden Door.

The vs. screen with Cain.

The upside-down pentagram on the ground.

A Horseman spawned during the first part of the boss fight.

Fallen Uriel spawned during the second part of the boss fight.

Mega Satan starting his final phase.

The final form of Mega Satan.

Mixed tears.

Mega Satan's flame breath.

Mega Satan defeated.

Mega Satan's Arena, revealed by the Debug console

These achievements are exclusive to Afterbirth and Afterbirth†.

Afterbirth added Completion Marks for defeating Mega Satan. In Rebirth, there are no achievements linked to Mega Satan.

Mega Satan does not have a health bar, making it difficult to determine how close he is to death.

Mega Satan does not drop a Golden Chest after beating him, cutting directly to Ending 16. It will drop a Golden chest if a portal to The Void appears, giving a choice of getting the ending or going to the true final floor.

Unlike normal bosses, he is immune to Midas' Touch.

Killing one of his hands deals 100 damage to Mega Satan.

With homing tears and The Ludovico Technique, the tear will be constantly attracted by the head even when it can't be targeted, making killing the horsemen, super sins, and angels very hard.

Unlocking the Golden Gate with the combined key pieces and then restarting the floor with Forget Me Now or an I AM ERROR room will waste the key, which will not respawn.

Mega Satan's battle theme is titled Hericide , [1] just like regular Satan.

, just like regular Satan. The Mega Satan room appears square but is a 1x2 room with a large pit where Mega Satan stands.

Bug! Doing too much damage between phases will cause the game to play the normal "boss defeated" music throughout the rest of the fight. Doing too much damage between phases will cause the game to play the normal "boss defeated" music throughout the rest of the fight.

Bug! If a If a Pickup spawns under Mega Satan's hand, the hand will start to move and rotate for the rest of the fight until it's pushed away. This is a purely cosmetic bug.

Bug! Using Using Delirious in Mega Satan's fight (after stepping on the pentagram), if Mama Gurdy is spawned, Mama Gurdy will be spawned behind Mega Satan, but it will be able to attack.





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