Cephalid Coliseum is a uncommon Land card from Modern Horizons 3 (MH3), collector number 300. Current market price: $0.30 (foil $0.40), TCGplayer market prices via Scryfall.
{T}: Add {U}. This land deals 1 damage to you. Threshold — {U}, {T}, Sacrifice this land: Target player draws three cards, then discards three cards. Activate only if there are seven or more cards in your graveyard.