Blood-Writ Bargain

This spell creates a pact which is enforced by celestial or fiendish forces. You and another willing creature commit to a mutual agreement, clearly declaring your parts of the agreement during the casting.

Until the spell ends, if for any reason either participant breaks the agreement or fails to uphold their part of the bargain, beings of celestial or fiendish origin appear within unoccupied spaces as close as possible to the participant who broke the bargain. The beings are hostile to the deal-breaking participant and attempt to kill them, as well as any creatures that defend them. When the dealbreaking participant is killed, or the spell's duration ends, the beings disappear in a flash of smoke.

The spellcaster chooses whether the beings are celestial or fiendish while casting the spell, and the Narrator chooses the exact creatures summoned (such as a couatl or 5 imps). There may be any number of beings, but their combined Challenge Rating can't exceed 5.