Apparently you can download an add-on that lets you recruit him. Probly from
www.teambg.com. And anyway id rather have an insane necromancer than a depressing enchanter like Xan.
Yes i just checked, The Darkest Day (Not currently compatible with ToB, but they say it will be soon) includes Xzar and Montaron, and Kagain and a few others. YES! typical it would be the biggest mod out there though.