Ghostblade Eidolon is a uncommon Enchantment Creature — Spirit card from The List (PLST), collector number C15-70. Current market price: $0.22, TCGplayer market prices via Scryfall.
Bestow {5}{W} (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.) Double strike (This creature deals both first-strike and regular combat damage.) Enchanted creature gets +1/+1 and has double strike.