Protective Sphere is a common Enchantment card from Invasion (INV), collector number 26. Current market price: $0.22 (foil $2.00), TCGplayer market prices via Scryfall.
{1}, Pay 1 life: Prevent all damage that would be dealt to you this turn by a source of your choice that shares a color with the mana spent on this activation cost. (Colorless mana prevents no damage.)