Feast upon the heart

When you devour the heart of an enemy you’ve helped to kill, you gain temporary hit points equal to its challenge rating, up to a maximum of twice your current level. 

Additionally if you eat the heart from a magical creature or a creature invested with magic (such as follower of dark gods) you gain the single use of a spell without any need for its verbal or material components (though you may still need to gesture). 

You can only hold one such spell at a time, and once used you’ll need to find another appropriate heart to consume to gain another spell. The saved spell will change if you eat the heart of a different magical being before using the one you currently have. 

The GM will choose the spell that you gain one use of, which may be up to 1/3 your level or the challenge rating of the creature, whichever is lower. (Anything below 1 will be a cantrip.)