Eldritch Devouring

You can perform quick deals with your patron to draw more magic out of the magic you already possess, and temporarily restore you when you do so.

• Increase your Charisma, Dexterity or Constitution scores by 1, to a maximum of 20. 
• As an action, you may consume a Pact Magic spell slot, expending it. If you do so, you gain two temporary spell slots. These spell slots are of a level equal to half the expended spell slot, rounded down, and they last until you finish a short or long rest. 
• Whenever you use your Eldritch Devouring or Mystic Arcanum features, you gain temporary hit points equal to half your warlock level + your Charisma modifier.