Gur-Rah, World's Elder

Eminence - As long as Gur-Rah, World's Elder is
in the command zone or on the battlefield, other
Giant spells you cast cost {1} less to cast.
Trample, Vigilance, and Double Strike
When Gur-Rah, World's Elder enters the battlefield, if you cast it, untap all lands
you control.