Trophy Collector (5e Feat)
From D&D Wiki
You can now collect 1 trophies for every enemy you kill(you must be the one dealing the killing blow) the more trophies you collect, the stronger you become as well.
Every 10 trophies : +1 to attack rolls
Every 15 trophies : +1 to damage rolls
Every 20 trophies : +5 to health
Every 50 trophies : +2 to attack rolls and +2 damage rolls