Is it possible to cancel a card like "Red Keep", who wants to influence an "Ambush" card, with "River Blockade". I´m not sure about "Ambush" whether it create a triggered effect.

Beornd said:

Well, you wouldn't be cancelling The Red Keep, but the ambush card anyway.

However, the FAQ states you can not cancel Ambush.

(4.14) Keywords Keyword effects with a point of initiation (such as ambush) cannot be canceled.

But using ambush is still a triggered effect, so your opponent cannot use ambush while Brienne PotS is in a challenge.

River blockade:

Cancel the first location effect triggered by an opponent each round.

Paying influence cost with a location is not a location effect.

Miklos said:

Thx - thats that what i want to here.