Squirrel Sanctuary is a uncommon Enchantment card from Modern Horizons 2 (MH2), collector number 174. Current market price: $0.38 (foil $1.46), TCGplayer market prices via Scryfall.
When this enchantment enters, create a 1/1 green Squirrel creature token. Whenever a nontoken creature you control dies, you may pay {1}. If you do, return this enchantment to its owner's hand.