See the Unwritten [Khans of Tarkir] Urza's Saga Monsters cannot be Special Summoned

Monsters cannot be Special Summoned from the Main Deck

if this card in face-up Defense Position

If you Tribute Summon a monster that includes "Ancient Gear" in its card name

Once per turn: You can target 1 face-up monster on the field: banish that target

Although these units typically suffered huge losses

See the Unwritten [Khans of Tarkir] Urza's Saga Monsters cannot be Special SummonedSet: Khans of Tarkir Type: Sorcery Rarity: Mythic Cost: {4}{G}{G} Reveal the top eight cards of your library. You may put a creature card from among them onto the battlefield. Put the rest into your graveyard. Ferocious If you control a creature with power 4 or greater, you may put two creature cards onto the battlefield instead of one.