I control Arya Stark with an attached Northern Courser, win a [MIL] challenge against a player who doesn't have a Title opposed to mine with Arya alone. Assuming there is a player with a Title opposed to mine, what happens when I trigger Arya's response?
Relevant text:
Arya Stark
Response: After you win a challenge in which Arya Stark attacked alone, each opponent with a Title that opposes your Title must also satisfy the Claim of that challenge, if able.
Northern Courser
If you win a [MIL] challenge in which attached character attacked alone, instead of the normal claim effects choose and kill 1 character controlled by the losing opponent.
As an additional question, with or without the Courser, how many times does the loser of the challenge have to satisfy claim if his Title is opposed to mine and I trigger Arya's response?