Illusion Ritual Spell

You have mastered Illusion spells, what is next?
== Walkthrough ==
Once you have reached 90 skill points in Illusion, a new conversation option is revealed when speaking with Drevis Neloren. If you ask him 
:"What else is there to be learned about Illusion magic?",
he will give you a spell called Vision of the Tenth Eye and send you to find four Master Illusion Texts scattered about the College.
Casting the new spell is the only way to see these books. They are in the following locations:
* Arcanaeum, on a table with The Legend of Red Eagle in the outer ring of the library.
* Hall of Attainment, at the top of the stairs on the landing under a bench.
* Hall of Countenance, on or near a barrel in the storage room (across from the room with .the arcane enchanter), on upper level in south-east cell.
* The Midden, on the same table as the Atronach Forge Manual.
=== Bring the Four Master Illusion texts to Drevis Neloren ===
After you have gathered all four of the books, return to Drevis and he will reward you with one master level spell tome (either Hysteria, Call to Arms, Harmony or Mayhem). Thereafter, Drevis Neloren will sell all the master level Illusion spell tomes.
de:Der Illusionsritualzauber