Sovereigns of Lost Alara is a rare Creature — Spirit card from Alara Reborn (ARB), collector number 12. Current market price: $0.82 (foil $9.75), TCGplayer market prices via Scryfall.
Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.) Whenever a creature you control attacks alone, you may search your library for an Aura card that could enchant that creature, put it onto the battlefield attached to that creature, then shuffle.