Cursed and Instill Fear

[vicidius]

Just recently starting playing ToME and unlocked the Cursed Class. Lots of fun! I've decided to invest mainly in the Endless Hunt and Gloom trees, so I've been putting lots of points in Willpower. So far it's been a pretty fun ride. Surprisingly successful with almost no activatable skills.

Anyway, just reached 10 and put points in Instill Fear and Heighten Fear. Everything was going fine until I noticed that certain types of monsters "ignore the fear." Slime/Jellies, Stone Trolls, Undead. Do they just have a naturally high resistance or are they just immune? Also, has anyone had any success with this type of build?

Thanks!