Taan is an ancient mage clan, once as powerful as the Vizjerei. They are more secretive and specialises in Skatsimi rites and magics.
Not much is known about this clan, besides the use of Skatsimi rites.
Known Taan Members
Ormus is a very likely member of the Taan clan, who helped Deckard Cain and heroes to use the Gidbinn Skatsimi dagger to protect Kurast from the encroaching jungle.
At first glimpse Cain thought he might be of the Taan clan, and later mentioned the Skatsimi specialisation among the Taan, which just so happens to coincide with the Skatsimi skills of Ormus.
Lam Esen was the writer of the Black Book, and very interested in Skatsimi magics. It's very possible he was a member of the Taan clan.