Gyarados (6/102) [Base Set Shadowless Unlimited] Ravnica Allegiance Mimic copies that attack including

Mimic copies that attack including its Energy cost and anything else required in order to use that attack

Set: Urza's Saga Type: Artifact Rarity: Uncommon Cost: {1} {1}

Set: Shadows over Innistrad Type: Creature — Zombie Rarity: Mythic Cost: {B}{B} Menace (This creature can't be blocked except by two or more creatures

Set: Dominaria Prerelease Promos Type: Enchantment — Saga Rarity: Mythic Cost: {1}{W}{W} (As this Saga enters and after your draw step

As long as Gaea's Liege is attacking

Gyarados (6/102) [Base Set Shadowless Unlimited] Ravnica Allegiance Mimic copies that attack includingSet: Base Set Shadowless Unlimited Type: Water Rarity: Holo Rare Retreat cost: Colorless,Colorless,Colorless