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, 2 August 2008
Flanking Action Battle: If your current army has more units than the current enemy army, bow one of your target Samurai there: The enemy leader targets and destroys a Personality in his army.
The Crab's Strength Battle: Target one of your opposed Crab Clan Personalities: Give him +4F. Until the battle ends, actions taken by enemy players that target him have the additional cost, "Discard a card."
If my opponent has used the Crab's Strength on his personality, then I use Flanking Action, if he chooses his personality that has been targeted by Crab's Strength, do I have to discard?
Thanks,
Brook Cunningham (rules official), 2 August 2008
Flanking Action Battle: If your current army has more units than the current enemy army, bow one of your target Samurai there: The enemy leader targets and destroys a Personality in his army.
The Crab's Strength Battle: Target one of your opposed Crab Clan Personalities: Give him +4F. Until the battle ends, actions taken by enemy players that target him have the additional cost, "Discard a card."
If my opponent has used the Crab's Strength on his personality, then I use Flanking Action, if he chooses his personality that has been targeted by Crab's Strength, do I have to discard?
Thanks,
No, you do not.
Required Targeting occurs before costs are paid, but the targeting of the enemy's Personality is not Required because you're not the one doing it:
http://rules.l5r.com/Abilities_and_actions#B._Required_Targeting (emphasis mine): "An action’s required targets consist of anything that is targeted by the player taking the action in the action's constraints or effects..."
So, that targeting happens as part of the Flanking Action's effects (Step D in "Using an ability"). Your opponent choosing his Crab Strength'd Personality will add the cost of "Discard a card" to your action. But, adding a cost during the effects won't force you to pay it because you've already passed the payment step (Step C), and it won't stop the effects from happening, because it was already checked whether you paid costs directly before any of your action's effects started resolving:
http://rules.l5r.com/Abilities_and_actions#D._Action_resolves: "If mandatory costs and required targeting have been met, activate the action’s effects in order."