Raging River [30th Anniversary Edition] Plains Island Sacrifice this artifact: Add {R}

Sacrifice this artifact: Add {R} or {G}

Then that player loses all unspent mana and you add the mana lost this way

Exile The Great Synthesis

then put any number of creature cards from your hand onto the battlefield

Raging River [30th Anniversary Edition] Plains Island Sacrifice this artifact: Add {R}Set: 30th Anniversary Edition Type: Enchantment Rarity: Rare Cost: {R}{R} Whenever one or more creatures you control attack, each defending player divides all creatures without flying they control into a "left" pile and a "right" pile. Then, for each attacking creature you control, choose "left" or "right." That creature can't be blocked this combat except by creatures with flying and creatures in a pile with the chosen label.