Here’s how co-op works in The Binding of Isaac: Rebirth
How is babby formed? We’ve long known thatThe Binding of Isaac: Rebirthwill have an all-new local cooperative feature but here are the specifics,as broken downby designer Edmund McMillen. When the second player presses start, they’ll randomly materialize as one of a variety of babies at the cost of a heart container from Isaac. When this happens, “both players’ damage/tears are lowered to balance things a bit, but every aspect of whatever items Isaac has at the time of spawning are applied to the baby, including usable items....