[Endoperez]

Lifeless are things that don't have any kind of metabolism. Ghouls are undead, but eat (humans, it seems). Wraiths are undead and lifeless - their body is reanimated to move, but it's not alive in any way. Soulless are zombies, mindless and lifeless and undead.

Not being able to heal is another matter entirely. Longdead don't heal. Once the bones are broken, there's nothing there. The exception to the rule are magical creatures (i.e. Magic Being tag) with the "does not heal" tag. They get back to full hp whenever they are in a province with a lab. Iron Dragons, as an example, get spare parts or something.

I think all constructs are lifeless. Sphinxes and Oracles are lifeless, as is that Iron Dragon.

I don't know all of what it does, but lifeless creatures are unaffected by regeneration and some effects like that, and perhaps "DIE" effects.