Bran stark says choose a non army non participating character that character is now defending on your side. Can I choose a character without a power icon to help defend a power challenge?

Bran stark says choose a non army non participating character that character is now defending on your side. Can I choose a character without a power icon to help defend a power challenge?

Yes. Having the icon is only a requirement for the declaration of an attacker/defender by the normal game framework. Bran bypasses this.