Stifle + Vines of Vastwood

[Mr. Safety]

Question from the Dreadstill thread: a player casts Phyrexian Dreadnought, his trigger goes on the stack, play Stifle to counter the trigger, opponent plays Vines of Vastwood on Dreadnought. Does this stop the Stifle from resolving? Is the Dreadnought the target of Stifle or is the trigger a separate entity on the stack?

Related note: can Emrakul's extra turn trigger be targeted with Stifle? I have done it with Nimble Obstructionist, but that's an activated ability, so it's different than a spell.

[H]

Question from the Dreadstill thread: a player casts Phyrexian Dreadnought, his trigger goes on the stack, play Stifle to counter the trigger, opponent plays Vines of Vastwood on Dreadnought. Does this stop the Stifle from resolving? Is the Dreadnought the target of Stifle or is the trigger a separate entity on the stack?

Stifle targets abilities on the stack, not on cards themselves. The fact that Dreanought cannot be targeted will be irrelevent for the purposes of Stifle resolving.


Related note: can Emrakul's extra turn trigger be targeted with Stifle? I have done it with Nimble Obstructionist, but that's an activated ability, so it's different than a spell.

Yes, for the same reason as above.

Note: Emrakul's ability of "protection from colored spells" is irrelevant in this regard anyway. The point at which Emrakul's ability triggered from being cast, Emrakul is not on the Battlefield and so the protection does nothing. For example, one could cast, say, Mana Drain on Emrakul. Emrakul cannot be countered, but you can imagine why one might do that. Alternatively, Emrakul itself being cast is a legal target for something like Mindbreak Trap, again, for the obvious reason that it doesn't counter spells, but exiles them.

[Mr. Safety]

That's what I thought, but I wanted to get a 2nd/experienced/judge opinion. Thank you!