Thopter Swarm

Improvise (Your artifacts can help cast this spell.
Each artifact you tap after you're done activating
mana abilities pays for {1}.)
Buyback {3} (You may pay an additional {3} as you
cast this spell. If you do, put this card into your hand
as it resolves.)
Create a 1/1 colorless Thopter artifact creature
token with flying.