Callidus Assassin is a rare Creature — Human Shapeshifter Assassin card from Warhammer 40,000 Commander (40K), collector number 109. Current market price: $4.45, TCGplayer market prices via Scryfall.
Flash Polymorphine — You may have this creature enter tapped as a copy of any creature on the battlefield, except it has "When this creature enters, destroy up to one other target creature with the same name as this creature."