[Bungleau]

I agree... it sounds like you are in the wizard/warrior path area.

When you entered that area, you were accosted by two spirits -- of the wizard and of the warrior, of course. When you killed them, each one dropped a crystal. In two rooms near where you found them were some disappearing staircases (when you entered the room, the stairs dropped into the floor). You need to use one of the dropped crystals on one of the rooms to get a little doll (jindol) at the top of the stairs. The crystal brings the stairs back.

You can only use one crystal, and each crystal works in only one spot. Look for a little lock-like mechanism on the side wall.

You can, if you follow Stackman's suggestions, build a staircase of your own to get up there. Use crates, barrels, and chests, and you can climb up without using the crystal.

Once you do that, you've got to use the jindol on one of the two urns in the path-choosing room. That opens the portcullis. Fortunately, you can use both jindols and open both paths if you want.

Xignal's site, as bsftcs pointed out, will give you much of this information with detailed pictures and walk-throughs.

Enjoy.