Aligned Hedron Network [Battle for Zendikar Prerelease Promos] Hydra Avatar sacrifice The Gitrog Monster unless

sacrifice The Gitrog Monster unless you sacrifice a land

Centaur Chieftain has "When Centaur Chieftain enters the battlefield

Its wings disturb more than air

Take an extra turn after this one if an opponent cast a blue spell this turn

Aligned Hedron Network [Battle for Zendikar Prerelease Promos] Hydra Avatar sacrifice The Gitrog Monster unlessSet: Battle for Zendikar Prerelease Promos Type: Artifact Rarity: Rare Cost: {4} When Aligned Hedron Network enters the battlefield, exile all creatures with power 5 or greater until Aligned Hedron Network leaves the battlefield. (Those creatures return under their owners' control.) The last hedron slotted into place, locking Ulamog in an infinite loop of binding energy.