Jalbert is a Redguard necromancer who can be found in his room inside Vilverin, and is likely protected by two Skeletons. He is fairly easy to take out, and if you are careful you can sneak up the stairs to his room and let at least one arrow fly into his unguarded back before he turns to fight you.
Jalbert's room contains some a note written by Jalbert, addressed to a sympathetic guard captain, praising him for secretly following the Necromancers' ideals and sympathizing and forgiving the him for having to pretend to pursue Jalbert when his company sighted him. No quest is activated by finding or reading the note. Judging from different parts of the letter the captain's name is probably Captain Aluc Cardius of Daggerfall in High Rock.
When leaving the room, if your security skill is low, a few leaps up some stones will get you past a difficult door and almost back to the point at which you first entered. A key to the door may also be found laying near a chest.
Jalbert is one of the few NPC's in the game who carries a pair of Black Wide Pants