His response let him be "declared as an attacker", but this attack is out of the usual timings... So, a question here: can other characters join his counter attack? (It does not read that he has to attack alone, like on other cards)

No-- The effect is to declare him as an attacker, meaning once you have resolved his effect (which you will do without interrupting yourself to do other things), you have now passed the opportunity in which characters can be declared as attackers (all characters would need to be declared simultaneously).

Thanks

I’m not sure I follow:

Ranged rules stipulate that a character can declare ranged attacks against these targets while its owner is declaring attacks, or it can participate in attacks that are declared by other players. In either case, the character must exhaust and meet any other requirements necessary to make the attack.

Grimbeorn's counterattack ability is not a Ranged attack, and other characters/players are not involved with it. What seems to be confusing? If you have a specific question in mind I'd be able to help better.

Card effects that allow you to declare attacks often include the step in which you declare attackers. For Grimbeorn, the cost (everything before the word "to" in his Response) includes the step of declaring him as the attacker. You, as a player, do not have a window in which you can declare attackers. The card effect does this for you.

Same goes for Quick Strike.

Note the difference with the Ambush trap: "Combat Action: The engaged player discards Ambush to declare an attack against the attached enemy." There is no language which declares an attacker for you. You do that step yourself, and can choose 1 or more attacks as you wish.

Thanks. For clarity I meant if Grimbeorn uses his ability to declare an attack, why can my partner player not use a ranged character to join the attack? I am basing my assumption that my partner player can on the rules I quoted in bold.

The FAQ Q&A on Quick Strike (well, one of them) is the reason a Ranged character can't join.

There is no opportunity for other characters to join a Quick Strike attack. One character is exhausted to pay for the cost of Quick Strike, and the effect is that the exhausted character is immediately declared as an attacker against the target enemy. The card's resolution does not allow for a standard declaration step in which other characters can declare.

As a practical matter, this seems to essentially mean that you are inserted into Player Attack Resolution at the action window after 6.8.1.

For reference, Grimbeorn's text:

Response : After Grimbeorn the Old defends an attack, spend 1 resource from his pool to declare him as an attacker against that enemy (and resolve his attack). The defending enemy gets -2[defense] for this attack.

And Quick Strike:

Action : Exhaust a character you control to immediately declare it as an attacker (and resolve its attack) against any eligible enemy target.

Thank you for this clarification...darn it! Have to replay my last quest again!

So can Grimbeorn use Bow of Yew if he is equipped with it?

He defends, spends a resource to declare himself as an attacker, exhausts bow of Yew to deal a damage and then resolves is attack?

13 minutes ago, David&Anna said:

So can Grimbeorn use Bow of Yew if he is equipped with it?

He defends, spends a resource to declare himself as an attacker, exhausts bow of Yew to deal a damage and then resolves is attack?

Yes. When you spend a resource he's DECLARED as an attacker so you'd be able to exhaust the bow and ping the enemy.

Cheers 😊