Flitterstep Eidolon is a uncommon Enchantment Creature — Spirit card from Born of the Gods (BNG), collector number 40. Current market price: $0.14 (foil $0.39), TCGplayer market prices via Scryfall.
Bestow {5}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.) This creature can't be blocked. Enchanted creature gets +1/+1 and can't be blocked.