I REMEMBERED. The unplaceable scene that was bothering me was actually from a King Arthur flick.
Queen Mab was leaving the castle of Morgana in company with Mordred; Morgana ran out, protesting that Mab was kidnapping her son. But the queen gestured and Morgana slipped, falling down several flights of stone stairs to her death. Mab's sidekick, a funny little gnome named Frick, bent crying over Morgana's prostrate form, because he had been falling in love with her. He explodes in anger at his mistress and Mab deprives him of his magic powers, leaving him alone and helpless in the world. "Why didn't you kill him, Auntie Mab?" asks Mordred. "Because that's what he wanted me to do," Mab replies with an arch look, and rides away.