A necromancer is a Thanaturge who has perfected the art of reanimating the dead, so much so that it is their primary means to complete their objectives, which typically include invasion, subjugation and domination. They have no upper limit to the number of undead they can maintain at any time, but any necromancer with more than a couple of animated undead will raise the attention of authorities and adventurers, if they have space to hide them a few hundred is possible, possibly even thousands.
Necromancers soon become a curse on the closest nations and as such often become the target for adventuring parties, those that fail however quickly bolster the forces of the necromancer. Ultimately a necromancer seeks to cheat death, a necromancer's eventual goal is to become an immortal Liche, with an army of thousands dedicated to keeping the Liche safe and ready to enslave a kingdom.
