Yoritomo Nishigori states:
Once per turn, if Nishigori is unbowed, produce 3 Gold which can only pay for a single Strategy's action.
I use that trait to pay for a Death of the Winds (2GC). What happens to the floating 1 gold?
Yoritomo Nishigori
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.
Yoritomo Nishigori states:
Once per turn, if Nishigori is unbowed, produce 3 Gold which can only pay for a single Strategy's action.
I use that trait to pay for a Death of the Winds (2GC). What happens to the floating 1 gold?
It is effectively lost. All 3 gold will "only pay for [that] single Strategy's action". The one extra exists, but it's restricted to only be allowed to pay for the action for which you don't need it because it only cost 2G, so there's nothing else you can do with it.