Vipers rage, Aegon's Hill question

By period3, in 2. AGoT Rules Discussion

The Viper's rage (Tales from the Red Keep) says:

Response: After you lose a challenge by 4 or more total STR as the defender, all characters controlled by the attacker lose a Military, an Intrigue, and a Power icon until the end of the phase.

Does this effect apply to all cards the attacking player has, or only to those participating in the attack?

Also, a question about Aegon's Hill:

"Challenges: Kneel Aegon's Hill to look at an opponent's hand. You may choose one character card in that hand and place it in its owner's dead pile."

What happens if the player chooses to discard a unique character from their opponent's hand when a copy of that unique character is already in play?

period3 said:

The Viper's rage (Tales from the Red Keep):

Does this effect apply to all cards the attacking player has, or only to those participating in the attack?

attacking participating

period3 said:

What happens if the player chooses to discard a unique character from their opponent's hand when a copy of that unique character is already in play?
in play