So... "Inhabitant"

I just spent the last five minutes and a crap-load of remedies possessing people. No achievement?

The way I did this was just to possess a rat and hang out in a tunnel for a while. The spell won't wear off while you're in the tunnel.

You won't get the achievement until after you leave the rat though, so just stay in there for a few minutes and then leave.

Awesome. I will attempt that, thank you.

My pleasure.