Is the Ability on Morning Frost Castle a mountain action?
Text "Mountain Battle/Open: Target two of your Personalities. Set the Force of one of them to that of the other."
Mountain Action?
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.
Any keywords on a card are inherited by its actions. Example: An action on a Ninja card is a Ninja action.
Citation
So abilities on a Mountain stronghold are Mountain abilities, and abilities on a Water Shugenja are Water abilities.