Shattered Kingdoms

It would be slow, but it's doable. My current character leveled from Master to GM purely by casting spells. (I didn't do any of the killing when I went with groups).

A priest would have to spend all of their XP they start with learning cure light and spam that constantly on people. It would take a long [REDACTED] time, but it is possible. In fact, I would bet so much on it, I might roll another priest just to prove it is possible.

sleeper

PS: Exploration experience actually makes this even easier than it was a year or two ago.

The thing is, I think there's a cap on non-combat XP per day. I don't know what it is, but I doubt you could get a level from it in one go. I'm not sure if that applies to healing, or just to stuff like rift/enchant armor/enchant weapon.

Well, ima try.

I wonder a way to train harm without killing something

That's easy.

Just don't try it with e-drain.