The Fifteenth Doctor (SLD-1584) (Borderless) [Secret Lair Drop]

Whenever The Fifteenth Doctor enters or attacks, mill three cards. You may put an artifact card with mana value 2 or 3 from among them into your hand.
The first nonartifact spell you cast each turn has improvise. (Your artifacts can help cast that spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)