There are ruins, scattered about the world, and all are sealed with unbreakable locks.
When all of these locks suddenly open, what emerges?
A cave with weapons sunken into the walls, blades sticking out of the floor and ceiling, and so on. Possibly, any weapon used in it could be torn out of the hand and sink into the stone.
Loud war-screams shatter the silence of the forest. The party, scrambling quickly over the thick forest floor, are ambushed by savage elves, dropping down from the trees and rock outcroppings. Their hair is cropped into mohawks and their arms are striped with tattoos.
They attack, and scalp unfortunate victims.