Playing Beneath the Stolen Lands with a solo Cleric (with an animal companion), I stumbled across a Wand of Death Ward, but it appears I can't use it, even though I should be able to.
* Cleric has Death Ward on the class list. (In particular, she even has one copy of this spell prepared.)
* Character doesn't have any ranks in Use Magic Device, but this shouldn't matter.
* Yet, despite the spell being on her class list, she can't actually use the want.

Why can't she use this wand?

Also, a couple other things I noticed:
* She has the option to cast Cure Critical Wounds, Mass in place of Mind Blank, even though Mind Blank is in her domain slot.
* She is not able to use a Scroll of Changestaff, even though she has access to that spell from one of her domains (Plant, which gives her access to the Barkskin spell).

This seems to be a bug. You can cast the spell, you should be able to use the wand.

The only explanation I can think of is that maybe the wand is treated as an arcane implement (Death Ward does appear on at least one arcane spellcaster spell list) and they restricted wands by arcane and divine spellcasters. Scrolls do have such a restriction, but wands should not so it's still a bug even if that case. That's a bug; spontaneous conversion of domain slots should not be possible, barring an archetype that lets you do so (I don't think there are any in Kingmaker?) This is technically correct. The way the rules for Domain spells work, you are given the ability to prepare them in special slots but they are not actually added to your class spell list. As a result you are not eligible to cast them from a scroll or wand. Most people would ignore this technicality at an actual tabletop game, but it is the way the rules work.

I have noticed the same issue in that dungeon. Both with a Death Ward wand, and some others. Forget exactly what now, but it was both for clerics and wizards. I was confused why they couldn't use them, or had to rely on a skill check (I have points into use magic device on the wizard).