Lifedrinker
Prerequisites Level 9, pact of the blade|xphb
Once per turn when you hit a creature with your pact weapon, you can deal an extra dice:1d6|noform|noparens|avg (1d6) Necrotic, Psychic, or Radiant damage (your choice) to the creature, and you can expend one of your Hit Point Dice to roll it and regain a number of Hit Points equal to the roll plus your Constitution modifier (minimum of 1 Hit Point).
Sources
Player’s Handbook (2024) p. 156. Available in the SRD