The Historian is located in the Underkingdom's UD Temple which is located southeast of the Bog.
Historian will jump around attacking at random. He will also cast a strong ice storm. There are scarab adds that attack and can poison.
All magic and melee work on him. Shurikens do not since he is a skeleton.
He is known to drop Feathers which carry a single charge of Resurrection. These feathers can be recharged within the UD temple (more information needed) as well as upgraded Thief gauntlets, and gems.