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A run of Isaac: Afterbirth as ???. All bosses defeated including the boss rush, Hush, The Lamb and Mega Satan.
Featured on Awesome Game Replays:    • Awesome Game Replays #15: The Binding...   - with commentary

To unlock the Boss Rush you must beat Isaac's Mom in under 20 minutes.
To Fight Hush you must beat It Lives in under 30 minutes.
To Reach Mega Satan you need two Key Pieces from defeated angels, or another means of opening the final door. Such as: Dad's Key or Get Out of Jail Free Card.

Character: ??? aka Blue Baby - Can only use soul hearts, regular red health won't work. A depleted soul heart is gone permanently and can't be refilled, you have to find new soul hearts to gain health. Health refill items don't work either.

I probably would've run out of time for Hush if I hadn't picked up Godhead in The Womb II. Clutchh

Items found: Speedball, Ball of Bandages, Chemical Peel, Satanic Bible, Pandora's Box, Magic Mushroom, Sad Onion, Evil Eye, Magic 8 Ball, Circle of Protection, Infestation 2, Match Book, Scatter Bombs, The Small Rock, The Negative, Book of Revelations, Box, GodHead, Mom's Eyeshadow, Capricorn, Guppy's Collar

8:10 Caves
17:00 Necropolis
22:30 Boss Rush
28:10 Womb
33:29 It Lives
33:50 Blue Womb (hidden floor)
35:22 Hush
39:00 Sheol
41:09 Satan
42:00 Dark Room
43:50 The Lamb
44:30 Mega Satan (no damage)