I think Logan has brought this up before, but I couldn't find a bug report here, so posting this for all our benefits after having confirmed the issue. Took Lintarith through the entire cave. Undead spawned. Destroyed the undead, but got no acknowledgment from the Mielikkians. No item drop either.

Check the "Dire boars". They drop a pendant. And there's no undead in that cave... are you sure you're in the right cave? (It's the one on the Rauvin Road - East... same area as the little grove)

Nope. Wrong. A Zombie Lord spawned with a regular Zombie. Those spawns may be similar to the Zombies that spawn only once per reset in the Lizard Caves, but I can assure you that they did and have done so before.

As for the dire boars, I'm pretty certain I checked every item drop from them as well and only got a bunch of meat for my trouble. I'll try it again.

Update: after two more runs through the cave, one of the dire boars finally managed to drop the item. The undead didn't reappear, so more than likely they're of the sort that only spawn once every reset.

Yes, there's an undead that spawns next to the backpack. Random red herring.

Probably someone used those default corpse placables that have some scripts to them that if someone comes too close, the damn thing disappears and spawns a zombie. Eh, doesn't really matter