Cult of Fierna

Fierna is a master manipulator. Mortals who desire success in love or who seek to become beloved leaders at the head of a band of fanatics are drawn to striking bargains with her.

Her cultists can gain the Infernal Loyalty trait. Cult leaders can also gain the Loyalty beyond Death trait.

Infernal Loyalty

This creature has advantage on saving throws while it can see a creature within 30 feet of it that has the Loyalty beyond Death trait.

Loyalty beyond Death (Recharges after a Short or Long Rest)

As a reaction when an ally this creature can see is reduced to 0 hit points, that ally is instead reduced to 1 hit point and gains temporary hit points equal to this creature's Charisma score + half its number of Hit Dice.