Troublesome Aid of Caiphon

When an ally grants you the grace of renewed health, you leverage your knowledge of Caiphon’s healing lore to gain even greater advantage than was offered—but at what price?

As a reaction, in addition to the normal number of hit points you regain from an allies healing spells, you regain a number of hit points equal to your Warlock level + your Charisma modifier as well. However, for the duration, you die after failing your second, rather than third, death save.