The Chained One

Warlocks are bound to serve their patrons and do their biddings. In return their patrons give them gifts of power, but some Warlocks go above and beyond offering the souls of those who they slaughtered in the name of their gods. when taking this feat if drop a creature to zero hit points you can offer their soul to the warlocks god. the warlock gains 1d10 + their spell casting modifier temporary hit points. if they offer more than one it goes up by 1d10 to a maximum of 3d10. you can do this as many times  equal to your charisma modifier.