Terbis, Roils the Earth

Whenever a land enters the battlefield untapped,
you may gain control of it.
Lands enter the battlefield tapped if Terbis is
tapped. They enter untapped if Terbis is
untapped.
Lands have "{2}, {t}: Tap or untap Terbis." This ability cost {1} less for you to activate for each five
lands you control.