The Time stone

Shroud
{4}: You gain control of this artifact. Any player
may activate this ability.
{x}, {t}: Return target nonland permanent with converted mana cost X or less to it's owners hand.
{x}, {t}: Untap up to X other permanents. Only activate if you control 3 or more Infinity Stones.
{x}{x}, {t}: Take up to X extra turns after this one. Infinity stones can't be untaped during any of
them. Only activate if you control 5 or more
Infinity Stones.