Grimhowl, Lich of Kederekt

Menace
When Grimhowl, Lich of Kederekt enters the battlefield, you may gain control of target creature, artefact, or planeswalker for as long as you control Grimhowl.
Permanents you control but don't own have
"{t}: Extract." (Sacrifice this permanent: Add all colored mana in its mana cost to your mana pool.)