There is a card (sorry, can't remember its name nor if it's an item or a spell - my friend owns the game, not me) that allows the player to open a gate at their current location.
If successful:
(1) should a doom token be added to the AO's track? I always though that new gate always = doom token, but I can't find anything in the rules to back that up.
(2) should monster(s) appear at the gate's location?
Doomer yes, monster not sure, most likely no. There is an Independence Square encounter that opens a gate, but that's not "a gate and a monster appears".
Some discussion on Naacaal Key:
I play that a new gate always adds a doom token and a monster, and that the Independence Square encounter was an oversight.
That's kind of true, it seems originally that whenever a gate opens, a monster pops out from it everytime. Except for the exceptions, obviously... 
like this OW encounter which says if you pull the lever another gate opens and you are drawn into this new other world and you have an encounter and all...
Hem said:
That's kind of true, it seems originally that whenever a gate opens, a monster pops out from it everytime. Except for the exceptions, obviously... like this OW encounter which says if you pull the lever another gate opens and you are drawn into this new other world and you have an encounter and all...
But that encounter is just flavor text. A gate can't open in the other world, and the text that the player should be concerned with is "A gate and monster appear!"
So there seems to be some consenus about a doom token being added to the AO's track when an investigator successfully plays Naacaal Key. I agree with this; however, I can't find anything in the RAW to support this claim. Specifically, I'm looking for something that says something like " *anytime* a gate appears in Arkham a doom token is added...", but I can't find anything like that. Am I just missing it, or is it not there?
Well, I don't think you'll find anything in the base game rulebook about "a gate and a monster appears" adding doomer either, but that's clarified in the FAQ.
Black Goat has a lot of items that do confusing or ambiguous things.
Dam said:
Well, I don't think you'll find anything in the base game rulebook about "a gate and a monster appears" adding doomer either, but that's clarified in the FAQ.
Yeah, that's my point actually. Does the fact that FFG explictly defines the case of "a gate and a monster appears = doom token" mean that the situation *doesn't* generalize to "any gate opening = doom"? Why wouldn't they just come out and say "any gate opening = doom"? I'd just feel more comfortable if my feeling that a doom token is added when Naacaal Key is successfully used was supported by RAW or FAQ.
I'm almost sure there was an official statement by Kevin that a doom token is always placed when a gate opens. However, that's some time ago.
The only passage in the AH rules you'll find is:
"Doom tokens are placed on the doom track on the Ancient One sheet as new gates open in Arkham." (page 3 / description of doom tokens)
It's a little vague, though, and sounds more like a general description, than a specific rule.