Polaris, Magnetic Manipulator

Flying, haste

Whenever Polaris, Magnetic Manipulator
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 Polaris.
(You expend 6 as you spend your sixth total mana to
cast spells during a turn.)