Dunno if this was suggested (too many pages), but should there be an ice cave of some sort there could be an nm that spawns as a reflection on the walls of ice which can be attacked to lure the nm out so that it can be battled.

If the party/alliance fails to damage the ice within a certain amount of time, the shadow could despawn and reappear 20min later. If the party/alliance deals enough damage within a given time period, the monster spawns just outside of the ice and can be battled like any other NM. Win/lose, the shadow could respawn 2-4 hours later. While the shadow is out and about, it could mess with unsuspecting adventurers in some way (maybe use an ice breath attack?)