It will take some time until you meet the Highpriest of the Ancients. He resides on top of the Tower of Illusion.
To get there you must not only master the tower itself.
Three sacred items must be collected only
to reach the Tower of Illusion.

If you manage to meet him you are truely worthy to take part in the Evolution Procedure.

And without Evolution you cannot finish your quest. So meet him under all circumstances.