Hmmm, maybe some battle power like Commune with the dead/Chorus of to create a magical protective circle which starts with 5% to 10% and added bonuses against undead. Arrows of bone will pierce anyone who steps close and 10% to 20% damage will be converted into hp boost.
A party made of dwarves and undead are gonna have a hard time getting around rivellon lol.
I love the idea of speaking with the dead as a skill, I also thought about resistance to cold and piercing damage but weak to fire and crushing. Y'know like a regular ol' skeleton.
I'm gonna suggest... maybe there'll be people willing to get you through, as long you get what they want or for a sum of "kaching".

That or you might have to navigate the dark alleys,sewers, abandoned houses, etc. and spend your time hiding in them. Or cast illusionary magic on yourselves to change your identities.
Fun identities: parents with a bunch of children (lol...)
Nun or monk trying to lead a bunch of people into safety