ToME: the Tales of Maj'Eyal

I made a skeleton temporal warden and escaped from the necromancer's tunnels to the overworld. Upon arrival (before even doing anything), I encountered an adventuring party NPC group. Normally, I'm used to these being friendly (on all my other characters). This time they were not. Additionally (and more problematic), the wizard apprentice outside Angolwen was hostile to me as well. I played for awhile and this never changed, making it impossible for me to save Derth and do Tempest Mountain, since I was not an antimagic character and couldn't get into Zigur. I'm guessing this is a bug, or is it supposed to be this way?

That's normal for Undead races. You are a Skeleton, how do you expect the NPC to react otherwise?
The first enemy drops a cloak of perception, which let's you disguise from npcs. Later on there's another and better way to hide your identity.