OK, either you go back the way you came, or there is another way. After you make the pledge to the Mavin Sword in the crypts, where do you go RIGHT after that? It seems you go back, but you can't since you jump down little holes to get there in the first place. I may sound confusing, but I am confused myself. If you actually understand, please post the answer.

You should see Rethpian on one side of the water. Remember the two portullises where you got the crystal and keys. There is a lever there that lets you out (left portcullis).

That's why, like someone said in this forum before..

"God I hate those camoflauged levers"

Spirit eye spell man, it is essential, not merely useful.