Pyreswipe Hawk (Bloomburrow Commander)

Creature — Elemental Bird - Flying, haste
Whenever this creature attacks, it gets +X/+0 until end of turn, where X is the greatest mana value among artifacts you control.
Whenever you expend 6, gain control of up to one target artifact for as long as you control this creature. (You expend 6 as you spend your sixth total mana to cast spells during a turn.)