Rotting Mastodon [Khans of Tarkir] Two-Headed Giant Tournament Harbor Serpent can't attack unless

Harbor Serpent can't attack unless there are five or more Islands on the battlefield

Set: Exodus Type: Enchantment Rarity: Rare Cost: {G} At the beginning of your end step

Set: The Brothers' War Tokens Type: Token Artifact Creature — Zombie Rarity: Common

except it's a white Zombie Snake Hydra with no mana cost

Rotting Mastodon [Khans of Tarkir] Two-Headed Giant Tournament Harbor Serpent can't attack unlessSet: Khans of Tarkir Type: Creature Zombie Elephant Rarity: Common Cost: {4}{B} Mastodons became extinct long ago, but foul forces of the Gurmag Swamp sometimes animate their decaying remains. The Sultai happily exploit such creatures but consider them inferior to their own necromantic creations.