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.
There is an important pair of fraternal twins. Possibly minor dieties, sorcerers, or maybe just an important pair of nobles. One is evil and one is good. The thing is, the one who looks evil at first glance is the good one, and vice versa.