The Wizard is a new peaceful villager mob added in the Thaumcraft. He can be found wearing royal purple robes with a gold symbol on the back, and a royal purple hat.

Wizards spawn in NPC villages, residing in Wizard Towers (see top-leftmost picture). Wizard Towers are composed primarily of cobblestone, have 2 glowstone blocks inside, Chiseled Stone Bricks (which are rare and are only found here, in a Barrows Hill and a jungle temple), and a chest. The chest has Thaumcraft 3 goodies, glass bottles, and sometimes other items from other mods such as Bronze Pants and a Bronze Pick from Industrial Craft 2. Another special thing in the chest is that it contains Knowledge Fragments. Knowledge Fragments are only found in Thaumcraft dungeons, the tower, and are sold by the Wizard himself. The Wizard will sell Knowledge Fragments and other Thaumcraft items for normal emeralds and can also buy other Thaumcraft items.

heres a video that show you the Thaumcraft Villager