"Fool, i can only be defeated by having the blade stabbed through my heart! As you are unworthy, you cannot kill me!"
a single crack loudly appears in the stone, the villain stares in shock, after a suspenseful pause the stone starts rapidly cracking further apart until it all falls off to reveal a gleaming flawless blade
"No! How can this be?! Have your journeys made you worthy?"
villain is stabbed to death yada yada yada.. after the protagonist gathers themself the blade suddenly sinks into the ground and they pull it out with a chunk at the end again. The power behind the blade starts talking to the protagonist
"Yeah no sorry, you're still not worthy, but eh fuck it it's been 500 years and that shithead needed to die, sorry to dissapoint. Please leave the sword somewhere accessible when you're done with it yeah?"
Gotta be careful with those impossible tasks. I let one of my players roll to convince a Wookie, that he spoke Wookie and to let them go, so of course he rolls a bunch of success (FFG dice are weird) and passes. Now I gotta explain how his character is faking speaking Wookie to a being that only speaks Wookie.