You start out near the center of the level. You will want to head to the cross-motif area in the northwest where you can collect the brass key. The hidden teleport to the north of the start is the quickest way to and from here. Now return to the start area with the key. The more northerly lozenge-shaped wall near the start contains the pentagram; the entire wall is actually a brass key door. From there, go down the nearest curved stair and through an illusionary wall to the exit chamber.