Coat of Arms is a rare Artifact card from Duel Decks: Mind vs. Might (DDS), collector number 58. Current market price: $18.93, TCGplayer market prices via Scryfall.
Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)