The pact of Asmodeus is non-canon in the mainstream D&D universe. _________________________________________________________________
The Arch-Devil of the Ninth Hell, Asmodeus accepts cultists that prove themselves to him in various manners. A cultist must change their alignment to chaotic-evil, and if necessary, change or remove any class features that require a specific alignment that contradicts chaotic-evil. When a cultist is bloodied or has just been killed, the player may activate the Pact of Asmodeus power, which allows the player to roll a d.20 and if they roll an 18 or above, they are restored to full health. If not, the power fails.
When a cultist dies, they are sent to the Ninth Hell as an undead servant of Asmodeus. The Dungeon Master will assign nine labors for the player to be tasked with- one assigned from each Arch-Devil-, and when all nine are completed, the user is formed in the real world in a new version of their body. If the player returns to life, they are considered undead. When a returned player is to die, they return to life after nine days. If their heart is removed and burned in an oath to a non-Devilish deity or sacred entity, they stay dead permanently.
This article does not exist in the canon D&D universe and is made as an add-on to Devilish-themed characters or storylines.