Hi! I keep finding snow fairies floating around. What can I do with them? What is the story behind the fairies? Thanks

Mostly just release them to get the achievements! You can also put them in your Minion Zoo or give them to your pets as a minion and/or treasure. If I get tired or overwhelmed (too many fairies in inventory), I just fragmentize them and use them to get more crystals to purchase items from the crystal shop.