Plaza of Heroes is a rare Land card from Dominaria United (DMU), collector number 421. Current market price: $8.89 (foil $10.05), TCGplayer market prices via Scryfall.
{T}: Add {C}. {T}: Add one mana of any color. Spend this mana only to cast a legendary spell. {T}: Add one mana of any color among legendary permanents you control. {3}, {T}, Exile this land: Target legendary creature gains hexproof and indestructible until end of turn.