Illusion Ritual Spell

Description
The Illusion Ritual Spell is the master-level spell-acquisition quest for the Illusion skill. It is obtained via a third conversation option from Drevis Neloren once Master level skill ranking is achieved. It involves finding 4 books scattered throughout the college that are visible and obtainable only by use of a novice-level spell that Drevis teaches once he's asked "What is the next step?" Vision of the Tenth Eye is a two-handed, 0 magika, illusion spell. As there are only a few main areas of the college - there is no book in the Midden Dark - the location of the books is fairly predictable; the walkthough below gives exact details. Drevis will respond to being told "Here are the texts you requested." with removal of the four books from the inventory and addition of one Spell Tome: Hysteria. The quest-specific dialog options are available only when all 4 books are brought to him, and he says "Yes, very good." "Here, then, is the first of the illusion spells you sought." He never does give the second, third, or fourth spells, but they instantly become available as purchasable Spell Tomes in his "for sale | Books" inventory: Call to Arms, Harmony, Mayhem.

Walkthrough
The books are located in the following areas:
 * 1) Hall of Countenance on the second floor, the store room directly to your right after coming up the stairwell. The book is on top of a barrel.
 * 2) Hall of Attainment on the second floor, right as you come to the top of the stairs, under a bench on the left side of the hall.
 * 3) The Arcanaeum Once inside the Arcanaeum, pass through the archway into the library proper.  Before you get to the three stairs down into the center, turn left into the outter ring.  The first table with two chairs on the right hand side is where the book is.
 * 4) The Midden. It will be in the middle of the table to the left of the Atronach Forge. (The big circle with candles all over, has an offering box).
 * 5) Here is a video walkthrough http://www.youtube.com/watch?v=kD38G18n4w4

Bugs

 * Sometimes, Drevis does not give the quest at level 90. If this happens, train to level 100 and he should give the quest. This might happen if the player reaches or surpasses level 90 with the help of the Oghma Infinium instead of leveling up by using illusion (needs confirmation). (Disproven, tested on character using Oghma Infinium to raise Illusion skill from 30 to 100 and was able to recieve the quest normally.)
 * The same glitch may occur by leveling using the muffle exploit. (Disproven, tested on character raising illusion from 20 to 100 and still got the quest normally.)
 * It may happen that one of the Master Illusion Text will not be in the location mention in the walkthrough above. This happen if player accept the Arniel's Endeavor quest while looking for book.