Let's say I reveal Valar Morghulis and I have Rhaegar Targaryen in play; however, I'm not First Player. Would my opponent, who is First Player, be able to trigger one response (i.e. saving a character he or she controls using a dupe or attachment such as Bodyguard) before I can trigger Rhaegar's response? Once Rhaegar's response is triggered no one else can be saved, correct? Characters with dupes would still die unless they cannot be killed for some reason, or am I wrong? Also, let's suppose I had saves on my other characters or wanted a character, such as Maester Aemon, to save himself. Would my opponent and I go back and forth triggering saves/responses until one of us decides to trigger Rhaegar's effect?

If my opponent declares Brienne of Tarth (PoTS) as an attacker or defender in a challenge can I Ambush a card or no?

FATMOUSE said:

Be careful here. Sounds like you are making a mistake by equating Save Responses and Rhaegar's "after he is killed" Response. They are not the same and are triggered at completely different times in the action window:

1. Initiate action: Valar activates
2. Save/Cancel to #1: ALL players can play AS MANY Responses that use the word "save" as they like.
3. Resolve action: Valar kills all characters not saved in #2 (assume Rhaegar was not saved)
4. Passives: deal with effects passively activated by anything in 1-3
5. Response: Use Responses (other than "saves") to anything in 1-4. THIS is where Rhaegar is triggered/resolved
6. End window.

So it doesn't matter who the First Player is. Every player can use as many dupes, Bodyguards, Iron Mines, whatever, as they want to save characters from Valar before Rhaegar ever dies and uses his Response.

FATMOUSE said:

Look at the way I outlined it above. By the time Rhaegar's Response is triggered (in #5), you've already had every opportunity to save characters from Valar as you like (in #2). You don't go back and forth triggering saves until one of you decides to trigger Rhaegar's effect; you go back and forth triggering saves before either of you even can trigger Rhaegar's effect.

You cannot use Rhaegar to effectively turn Valar into "cannot be saved." The timing of it does not work.

FATMOUSE said:

You cannot. Ambush counts as a triggered effect, even though it cannot be canceled (because keywords cannot be canceled). Brienne stops opponents from triggering anything.

Many thanks, ktom.