The first details for the upcoming expansion to The Binding of Isaac: Rebirth were revealed today by Edmund McMillen. The DLC will be called Afterbirth and will feature a metric crapload of new content.
- 100+ new items
- a full new game mode that will totally change how you play
- 10 new challenges
- a new playable character
- a new alternate final chapter
- new alt floors
- new game endings
- new final bosses
- tons of new bosses and enemies
- new item pickups, cards, pills, etc.
- tons of new achievements and rewards for beating the game on hard
- new co-op babies
- new transformations
- and more… :|

Word is that this new content should "easily extend the gameplay time by another 100-200 hours." McMillen also notes that some of the following ideas may make it into the game as new challenges. These are the top 9 suggestions they received from fans but it's important to note that not all of them may make it into the game.
1. a XXXL room challenge: all floors are XL but have the max amount of rooms per XL floor.
2. High Speed!: the game plays at x2 speed
3. Sonic: all doors are arcade doors, start with 99 coins all enemies have greed shot effect (cause you to drop/loose coins) you die at 0 coins.
4. Max hearts : a challenge where you start with max heart containers but hearts no longer drop.
5. High Rule: start with moms knife + trinity shield + boomerang
6. Rollers: each time you complete a room all of your items and stats are rerolled (item pools arent depleted)
7. BRAINS! : start with 3-4 bobs brains, blindfolded (no tears)
8. Blue Bomber: blue baby run with kamikaze + flying + new dlc item + pyromaniac, Blindfolded (no tears)
9. all start boss rush: a challenge where you fight all the games bosses

Well, those just sound delightful. McMillen hopes that Afterbirth will be released "sometime this year."