Greatjon Umber can he be used in an attack\defense against antother player

By Ulrictar, in 2. AGoT Rules Discussion

Hi

The card says:

Greatjon Umber says: Challenges: kneel to have Greatjon Umber participate in the current MIL or POW challenge as either the attacker or as the defender.

If two other player are having a challenge that I am not involved in could I kneel GreatJon to have him participate in that challenge

Ulrictar

yes