Stonekeep

You can pass through fire unharmed by walking up to it, turning your back to it, and walk backwards through the fire.

In the first room of the game, pull the lever by the door down, then up, then down again.
Head south to the wall.
Proceed east until you hit the wall there.
Go two square to the north.
There should be a secret crack to the west.
Inside the crack is a lever.
Pulling it will activate a secret passage to the south.
Inside this crevice are three oil grenades, and another secret crevice on the north wall.
Inside the crevice is a magical dagger which really kicks ass.
(Information from Cheat Machine)