So my friends and I are pretty sure we have never played this game completely right yet and there are a few things we are trying to figure out. The biggest thing is when cards are effected by other cards "in play" does that refer to cards that only you control or that anyone controls? The biggest example we have is the core set Grey Wind. It says "If Robb Stark is in play, lower the cost to play Grey Wind by 2". If one of my opponents has a Robb Stark in play can I lower Grey Wind's cost or do I have to have a Robb Stark under my control to lower the cost?

Is Robb Stark in play?

Yes. There is a Robb Stark in play controlled by your opponent.

Thus Grey Wind's cost may be lowered.

Don't read restrictions into the cards that aren't there.

Thanks. That's what we thought but it seemed almost too good to be true. And I think I am safe in assuming then that passive abilities like the core set Lady's text that says Sansa Stark gets +1 strength and renown would apply to opponents Sansas if they had her out correct?

Yes, for the same reason you get to reduce Lady's cost if Sansa is in play.

The only general exception to this are self referential cards (there's a specific entry on them in the FAQ). If a card refers to itself by name, it refers only to itself (and not other copies in play with the same name).

An example is "Cersei Lannister" ("Cersei Lannister does not kneel to attack in intrigue challenges") wouldn't grant an opponent's Cersei that same ability.

Just be aware that when a card uses it's own title, it is referring to just itself, not all cards with the same title.

Now the question I have about the core set varys is if you trigger his effect after new plots are revealed to the when revealed effects resolve first and then the plots change hands or is using varys ability considered a response to the when revealed effects taking effect?

Varys's ability is not a "Response", it's a "Plot" (and therefore a player action). It's definitely not a save/cancel response, so it can't interrupt the resolution of the plot, and as a player action can only be used in the player action windows in the plot phase - entirely separate from the framework actions of picking plots (for more info, see the flow chart in the FAQ for timing).

That clears things up for me thanks.