I got a wired situation here. One player used his Brienne of Tarth to initial a millitary challenge to a martell opponent and won. The martell player chose his The Red Viper to die. Can he use a duplicate to save the Red Viper? I think he can because the Red Viper immunes Brienne's ability and using a duplicate to save himself is a gained ability of the Red Viper. But someone doesn't agree with me because he thinks Briennes's effect affects just the person who's playing the game, not any card in play.

Whos's right?

Brienne of Tarth: While Brienne of Tarth is participating in a challenge, opponents cannot trigger effects.

The Red Viper: Immune to events and character abilities.

bearwangpp said:

Your friend has the right of this. Immunity only protects a card from effects that interact directly with it. Brienne clearly doesn't interact with TRV, she interacts with her controller's opponents.

That only the immune card itself is protected by the immunity is an important point that is not fully understood by a lot of players.

Some examples:

You could steal a power from TRV with Ellaria Sand, because only TRV is protected by the immunity, not the power counters that are on him.

You could discard a duplicate attached to TRV with Ser Axel Florent, because only TRV is protected by the immunity, not any duplicates attached to him.

If a duplicate is discarded from TRV to save him, you could use Seasick or other appropriate cancels to cancel the save effect, because only TRV is protected by the immunity, not any effects originating from him.

I can understand your examples, but i don't think it can explain my question.

In the official FAQ, there is "Specifically: The effects of a character ability cannot be applied to a card that is immune to character abilities."

I treat this phrase as TRV can be played just as Brienne is not exist.

bearwangpp said:

"When determining immunity to event cards
and character abilities, check the effect of each
card. A card's immunity only extends to effects
that would ordinarily be applied to cards of the
immune card's type."

So, check the effects of Brienne. What part of "While Brienne of Tarth is participating in a challenge, opponents cannot trigger effects." is being applied to character cards? None, right? Because Brienne doesn't even mention character cards. She mentions, and works on, opponents.

Granted, there is an indirect effect on characters - that the opponent who controls them cannot trigger their abilities - but that is not the same thing as Brienne being applied to the character card. For example, let's say I play an event Nighttime Raid ("Choose an attacking GJ character you control. Until the end of the phase, that character gains stealth.) on one of my characters, then use that new Stealth to bypass the Red Viper. Does TRV treat my character as if the event had never been played, and therefore as if my character doesn't have Stealth, because of his immunity to events? No, because my event was played on a different character, who then went after TRV with something he is not immune to - a keyword. My event directly affected my character thus indirectly affecting your Viper, so the Viper's immunity to events does not help because the event itself did not do anything (directly) to TRV.

Same situation with Brienne. Her character ability works on and directly affects the opponent thus indirectly affecting all of the opponent's triggered effect. Any immunity on the cards of those triggered effects is too remote from the direct effect on the opponent to do anything.