Huh, that's potentially very useful, especially if an opponent decides to do combat first, as it'll basically deny them their turn.
It ends the combat phase. How does it waste their whole turn?
Because they can't play any spells anymore. Sure they can still activate abilities, but most abilities are instand speed anyway, so they could also do that during your turn.
So if the opponent is not playing anything during his first mainphase, he skips his whole turn after the draw phase.
Because they can't play any spells anymore. Sure they can still activate abilities, but most abilities are instand speed anyway, so they could also do that during your turn.
So if the opponent is not playing anything during his first mainphase, he skips his whole turn after the draw phase.
Edit: *their first mainphase / *they skip