I had another strange thing happen to me with a thrall cage in a small Accursed camp in I5. A Stygian Invader in full armor was in the cage. I have never seen a fully armored thrall in one of the regular thrall cages except for named bearers.

It is bad enough that newly-freed thralls have somehow smuggled weapons into the cages with them, but full armor and weapons is a bit immersion-breaking.