Countering Spells

[BobLoblaw]

Are you able to counter a spell with a non-counter spell, or does a new stack have to be formed? For example, if someone played a negative spell, can one respond with vines of vastwood, or would vines of vastwood need to be played first to offer protection? If that is allowed, and someone got a vines of vastwood ontop of a negative spell, could someone then throw an unsummon ontop of the vines of vastwood to cancel them all out? Or would the unsummon have to be a newly started stack?

[Arix]

The stack resolves in LIFO order - last in, first out. Say you cast a Lightning Bolt on my creature, then I use Vines of Vastwood in response. Since the Vines was the last thing played, it's the first to resolve. Then your Bolt tries to resolve, but its target is illegal, therefore it's countered. If you cast Unsummon in response to my Vines, Unsummon will resolve first and bounce the creature, then Vines would be countered, then Bolt would be countered.