Avatar of Might is a rare Creature — Avatar card from Prophecy (PCY), collector number 109. Current market price: $1.65 (foil $54.99), TCGplayer market prices via Scryfall.
If an opponent controls at least four more creatures than you, this spell costs {6} less to cast. Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)