Guild Wars 2

On Blackgate, the skill challenge states to defeat the brood mother and her brood. Upon attacking her the brood never spawned. Upon defeating her, she turns green and unresponsive/non-interactable. Her orange event skull and circle still show up on the map around her and no brood spawned in her cave or on the levels above her, making it impossible to finish the challenge and unlock the zone.

As of October 14, this is still bugged.

Ok after a bit more investigation, you need to dive deep in the pool next to the Broodmother to find her last hatchling. Once you kill it, the skill event is complete.