This item is used to Reform Evolve certain Pokémon. Namely, Snorunt and Kirlia (both of which also have Natural Evolutions as well). And when they evolve, both of them change types! They also have different stats from their natural evolutions, and have different movepools!
...Wait a second, how do you reverse the evolutions?
Also, you can randomly find Dawn Stones after battles (with Pickup, of course)!
...Sorry, I was bored.