Diablo 4 has a fetch quest in the Scosglen region called Stolen Artifice, in which an NPC named Merryn sends you out from Braestaig to retrieve an item from a thief called Darcel. It's a runic charm that was being used to help an ailing mother and child recover, until Darcel and his thugs stole it. The jerks.
This is supposed to be a typical sidequest, nothing too major, but players were finding it unusually hard. Instead of having to fight one Darcel, they were encountering dozens of Darcel doppelgangers. Though some managed to figure out which one was the original and kill him to complete the quest, others were forced to retreat and return, sometimes finding that hundreds of Darcels had spawned in their absence.
While some players put forward a theory that the issue was a bug with the summon minions ability elites can have, Darcel isn't one of those. He's just a large man with a spiked mace and a bunch of hit points. Players with some of the more overpowered Diablo 4 builds like lightning sorcerer had fun testing themselves against the barmy Darcel army, though in terms of loot it wasn't really worth it.
Blizzard responded by disabling the Stolen Artifice sidequest until it could be fixed. Which it has. Hotfix 3, issued on June 4, dealt with the multiple Darcels bug, as well as one where Astaroth would destroy a house before even arriving at it in the quest As the World Burns, and some stability issues. As a server-side hotfix, your client won't need to be updated to apply these changes. Goodbye, Darcels. We bear-ly knew you.