Githas, Mobile Citadel

Githas, Mobile Citadel enters the battlefield
tapped and doesn't untap on your untap phase.
Pay 10 life: Untap Githas, Mobile Citadel.
Cumulative upkeep: Pay 10 life and {w}{u}{b}{r}{g}
When Githas, Mobile Citadel deals combat
damage to a player, that player taps all
creatures he or she controls, they do not untap on
his or her next untap phase.