D20 Wonderment Mechanics

COST/REQ: Essence

Anchored: A character with no more than their lowest Proficiency Bonus and at least one measure of Aptitude may exchange 1 untainted and uncorrupted Free Essence per Long Rest to have a killing blow or effect drop them to 1 HP instead.

iCore Wonderment Mechanics

Type: Physical

If you are having trouble thinking how this might play out after reading this, check out the Players Roleplaying Guidance content (or ask the Game Master how it is best expressed in the setting).