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, 13 February 2012
Hello,
Can Mastering the Elements copy a unique spell like Unnatural Flood?
Mastering the Elements: Text Unique Reaction: After this card enters play, target your Spell and pay Gold equal to its base Gold Cost: This card permanently copies the Spell's keywords, traits, and its base abilities that do not themselves copy abilities.
Unnatural Flood: Text Water • Unique Battle: Bow this Shugenja and target an enemy Personality: Move him home; if this Shugenja is Water, this movement will not be negated. If the target moved, bow him and negate his (future) movement.
Brook Cunningham (rules official), 13 February 2012
Can Mastering the Elements copy a unique spell like Unnatural Flood?
Yes, indeed.
No Rule or any card text prevents that.
Alex Jones (rules official), 13 February 2012
Note errata has been issued for Mastering the Elements, whose ability now reads: Reaction: Once per game, after this card enters play, target your Spell and pay Gold equal to its base Gold Cost: This card permanently copies the Spell's keywords, traits, and its base abilities that do not themselves copy abilities.
Alex