Hm eventually some homebrew variant of a rust Monster? That would be for a gory death, his Skeleton dissolving and leaving a heap of flesh.![]()
Although the bones aren't effected by the rust unless there are severe wounds exposing them.
Death within a month unless they also have matching regeneration powers.
I have Howlett now as a dwarf with Dwarven Fortitude but am now considering making him a troll or trollkin runt.
Resistance to Bashing.
+1 to AC.
The main benefit of a metal skeleton is having a much harder time breaking bones, and to a much lesser extent having a harder time getting to the soft squishy bits inside your rib cage / shoulder blades because those bones won't shatter. But the skeleton doesn't do anything to stop tissue damage, blood loss, or tender organs getting punctured and leaking vital fluids all over the place. In fact, there's no good reason to give them immunity to critical hits in general, unless the only critical hits you can imagine are broken bones.
So Resistance to Bashing because bones cannot break, and +1 to AC because the bones do provide some minimal protection against weapons penetrating the rib cage / shoulder blades. But even that is stretching things. A bludgeoning hit to the head should still do horrible damage as the brain is smushed by the transfer of force.
Also, you know, the whole horrible death because his skeleton is metal. But I'm guessing you're handwaving that part because "A Wizard Did It."
My reticence to improving AC is that he'd have to take damage before an attack hit the unbreakable bones.