Undead lore and Demon lore
There is no way to know if it is possible to tame a demon or undead. I hope you will add an analogue of the "Beast lore" spell for demons and undead. This is a small but very important detail.
This would be cool. As it is, the only way to know if you can tame one is to try
more ways to find out in game the different additions the Dev's have put in!