This mod adds the 3 main hearts from the game "Binding Of Isaac: Rebirth"

The Hearts included: Soul Hearts(Blue) - Absorb 2 damage (like a regular heart) and then disappear. Black Hearts(Black) - Absorb 2 damage and you do damage around to enemies around you when you lose that heart. Eternal Hearts(White) - Gain a new permanent red heart after not being damaged for 10 minutes.

After killing monsters, there's a low chance that they will drop one of the 3 hearts

If you walk over the heart item (or use it as an item, configurable) then you will get that heart added to you.