Heartbreaker

This mod adds a single item, and four mechanics along with it, firstly; damage that you take cannot be healed, and your hearts are lost as soon as your invincibility frames are gone, secondly; damage dealt to mobs heals you slightly, but damage to players will heal you substantially more, granted it's in the invincibility period; third, kills to mobs will steal a third of their remaining health as yours, but player kills will steal all their remaining health; last mechanic, when you die, you lose half a heart, permanently...unless you use the only item in this mod, the Life Crystal, which grants 1 heart and reduces the death penalty by 2, so it's like half a permanent heart, and when you are out of hearts...well, it's time to delete this world.