Clash of Realities is a rare Enchantment card from Betrayers of Kamigawa (BOK), collector number 97. Current market price: $0.47 (foil $2.12), TCGplayer market prices via Scryfall.
All Spirits have "When this permanent enters, you may have it deal 3 damage to target non-Spirit creature." Non-Spirit creatures have "When this creature enters, you may have it deal 3 damage to target Spirit creature."