The Ice Will-o'-the-Wisp can be parked on the South Han Cape Village Snow Trail (morning and night water), the East Han Cape Village Snow Trail (morning and night water), the Prison Tunnel, Frigit Prison Island - Entrance -, and Frigit Prison Island - Capture everywhere.
Its strength is 2, its specialty skill is freezing bombs, and its attack method is ice. It can be processed into nutritional soup*1 and used as a prop for players.
These contents are summarized from the fact sheet, and I believe they can answer your questions on this issue. There are more high-quality guides about Octopath Traveler 2 on this website, you are welcome to check them out at any time.