It reads: Response: After attached hero participates in an attack that destroys an enemy, exhaust Rohan Warhorse to ready attached hero.

This does not work when the hero attacks alone right? There always needs to be +1 character at least, correct? Can I cause Westfold Horse-breeder to participate in the attack although she has 0 attack?

It works when the hero attacks alone. If you attack, you participate in the attack whether other characters are participating or not.

It doesn't matter how many characters attack to trigger Rohan Warhorse. You can only declare the attached hero as the attacker for the attack the Warhorse initiates.

Yes, you may declare the Horse-breeder as an attacker, but she only has zero attack; so not the best idea.

1 hour ago, Wandalf the Gizzard said:

It doesn't matter how many characters attack to trigger Rohan Warhorse. You can only declare the attached hero as the attacker for the attack the Warhorse initiates.

The warhorse does not initiate an attack, just readies the character -- which frees the character to make another attack on a different enemy (with or without others), or do anything else that requires exhaustion.

Thanks everyone!

Sorry to bring this back up, but according to Merry's (tactics) ability again : Response: After Merry participates in an attack that destroys an enemy, ready another character that participated in that attack. Doesn't this make it clear that "participates" means more than one attackers and therefore Rohan Warhorse doesn't work with only one attacker?

The operative word that makes Merry's power plural is "another", not "participates". It is possible to be the only participant in something.

If you replaced the word "another" with "a", Merry could attack by himself, destroy an enemy, and ready himself. Repeat infinitely.

I see. Thanks again guys!