Academy Ruins [Secret Lair: Heads I Win, Tails You Lose] Swamp Mountain if you didn't cast it

if you didn't cast it from your hand

000 Type: Artifact Creature — Necron Rarity: Rare Cost: {3}{B}{B} Flash

mill three cards

Polymorphine — You may have Callidus Assassin enter the battlefield tapped as a copy of any creature on the battlefield

If excess damage would be dealt to that creature this way

Academy Ruins [Secret Lair: Heads I Win, Tails You Lose] Swamp Mountain if you didn't cast itSet: Secret Lair: Heads I Win, Tails You Lose Type: Legendary Land Rarity: Rare {T}: Add {C}. {1}{U}, {T}: Put target artifact card from your graveyard on top of your library. Its secrets once wrought the greatest artifice ever known. Now crabs loot the rubble to decorate their shells.