Gift of the Protectors

[ Don des protecteurs ]
Prerequisite: 9th-level warlock, Pact of the Tome feature

Description not available (not OGL).
But here is a summary:

A creature that has written its name on your Book of Shadows drops to 1 hp when reduced to 0 hp (1/long rest).
Tasha´s Cauldron of Everything
  1. DnD 5e Eldritch Invocations › Gift of the Protectors