From publisher blurb:
A 5th Edition Mini-Dungeon adventure for 3 characters of level 7
The Hall of the Hellbound Heart is the dangerous domain of Asmætheon—an aspiring necromancer of some infamy. Secluded away and isolated from all save his servants, Asmætheon has been slowly harvesting the hearts of local tieflings, from which he has constructed a black heart, which he intends to preserve and use as his phylactery. When the characters finally arrive at his hall, he is away. His servants and guardians, however, are not.