A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 11 December 2010
Kuon attacks alone, Phoenix player with City of Tears defends.
As first action, the defender attachs Consumed by Five Fires, reacts with Heavenly Yari of the Phoenix targeting Kuon, which doesnt happen because of Kuon's trait, and then goes to take the aditional battle action to use Consumed by Five Fires to destroy Kuon.
Is this play legal? The only doubt I have is that both the additional battle action and the reaction of the Yari have the same trigger:
Relevant card text: Heavenly Yari of the Phoenix Reaction: After the resolution of an action whose effects attached a Spell from your hand, bow this card: Straighten a target Personality. Give him +2F.
City of Tears Equipping Spells is a Battle/Open action for you. After the resolution of an Equip Battle action you took, you may take an additional Battle action from the Spell it attached.
Hida Kuon (Experienced 6) After the first time each battle another player's action targets Kuon: If he is the only Personality in his army, the action's (remaining) effects do not happen.
Brook Cunningham (rules official), 11 December 2010
Kuon attacks alone, Phoenix player with City of Tears defends.
As first action, the defender attachs Consumed by Five Fires, reacts with Heavenly Yari of the Phoenix targeting Kuon, which doesnt happen because of Kuon's trait, and then goes to take the aditional battle action to use Consumed by Five Fires to destroy Kuon.
Is this play legal?
Yes, this play is legal.
Additional Action: "When an action or triggered trait grants an additional action, the timing of the additional action is delayed, such that the action is taken once the action or trait that granted it has ended, and the opportunity to play Reactions to the end of the action or trait has passed. This makes sure that Battle actions can not occur within other Battle actions, and so on."
Thus, after the Equip action resolves, both the triggered trait of the Stronghold and the Reaction of the Yari are taken and resolve their effects, and then the additional action granted by the former is taken.