I deal damage to opponent with my Whirling Dervish
he then takes control of it with Captivating Vampire
Will the Dervish (now under opponent's control) still get a +1/+1 counter at end of turn?
I deal damage to opponent with my Whirling Dervish
he then takes control of it with Captivating Vampire
Will the Dervish (now under opponent's control) still get a +1/+1 counter at end of turn?
No. Since he controls it when the ability would trigger, the "opponent" refers to hid opponent, you. Since it didn't hit you that turn, the ability doesn't trigger.
Also note that Whirling Dervish has protection from black, so it can't be taken by Captivating Vampire anyway.
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isn't it a delayed trigger event though that would go on stack regardless of who is "opponent" in end of turn?
No. That would be if it were worded more along the lines of "Whenever Whirling Dervish deals damage to an opponent, put a +1/+1 counter on it at end of turn".
Fluttershy is best pony.
but when it dealt the damage it was dealing it to an opponent??
Doesn't matter.
Fluttershy is best pony.
I think some uncharted waters is that up until now an opponent was always a player, but now in innistrad they introduced cards that make creatures fight each other (like prey upon) so now a creature can also be an opponent? so if the whirling delvish fights another creature and deals damage to it does ability trigger? has wizards addressed this yet?
They haven't addressed it because nothing changed about opponents -- an opponent is still only ever a player.
The term "fight" is just new wording for an old ability that merely causes two creatures to deal damage to each other. This doesn't count as combat damage, and isn't considered combat by any means. As such, this isn't a case of a creature attacking another creature - that still can't happen.
can planeswalker be an opponent?
Nope. That's never been the case. Just as a refresher, here's what the comprehensive rules have to say about opponents:
And then, going back to rules 102.2 and 102.3:Opponent
Someone a player is playing against. See rules 102.2 and 102.3.
If an opponent meant anything other than a player, it would be covered in the comprehensive rules. As you can see, your opponents are always going to be other players.102.2. In a two-player game, a player‘s opponent is the other player.
102.3. In a multiplayer game between teams, a player‘s teammates are the other players on his or her
team, and the player‘s opponents are all players not on his or her team.
Driving the point home -- if your creature enchanted with Curiosity attacks a planeswalker, you don't get to draw a card, because a planeswalker is never considered your opponent.
what if it is a multiplayer game, and the opponent that was dealt damage has left the game before the ability is supposed to trigger?
It still gets the counter.
Fluttershy is best pony.
Wtf but you just said the opponent matters only at end of turn? So if opponent is different or not there it won't get counter? Why did u changed your mind?
I didn't change my mind at all. It's a completely different question with a completely different answer.
Fluttershy is best pony.