Undead siege came in and just sat around like usual, but started attacking wildlife.

Necromancer raised an "Elk Bird Head" at which started attacking the necromancer and undead. The entire siege of 80 undead started attacking and hurting it, but it seems indestructible.

Now 80 undead are clustered in a tight 3x3 space and simulator speed is down to a crawl from the constant fighting.

I think it is training the undead.