Nail to the sky is a very high level spell that reverses gravity on an object, making the object repel off of the ground and fly off into the sky and into orbit. When used against most players they get a chance to avoid it, and if struck by it they get a few chances to break out as the fly into the air. It also doesn’t work against flying creatures. That said… it’s generally an instant kill spell even if they do manage to save before orbit, but it’s also used with feather fall spells for fun fast travel almost anywhere on the surface.