Time Stone

If Time Stone would become untapped while it has a burden counter, instead remove a burden counter from it.
{t},{1}{u}: Time Travel. Untap Time Stone.
{t},{2}{u}, put a burden counter on Time Stone: return target permanent card in a graveyard that was put there from the battlefield this turn to the battlefield under its owner's control.
{t},{7}{u}{u}, put three burden counters on Time Stone: Take two extra turns after this one.