The Animator's sudden heart attack.
The Animator was a character in the film Monty Python and the Holy Grail, portrayed by Terry Gilliam.
He was the animator of the Legendary Black Beast of Aaaaargghh, which attacked King Arthur and his knights in the cave where the location of the Grail was written onto the wall. The knights only managed to escape when the weak-hearted animator suddenly died of a fatal heart attack, stopping and ending the beast forever.