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, 26 October 2012
Does Wide Valley stop the "unit destruction" of A Stain Cleansed (or similar unit kill effect)?
Wide Valley (trait) Before an action's effect destroys a card in a unit: Negate the destruction.
A Stain Cleansed Battle: Choose your performing unbowed Magistrate, target an enemy card without attachments or an enemy unit, and pay Gold equal to the card or unit's total Gold Cost minus 2: Destroy it.
Wide Valley negates the destruction of a card... but not of a unit. Is there a Rulebook clarification of unit kill being multiple card destruction or is it labeled separately?
Alex Jones (rules official), 28 October 2012
Does Wide Valley stop the "unit destruction" of A Stain Cleansed (or similar unit kill effect)?
Wide Valley (trait) Before an action's effect destroys a card in a unit: Negate the destruction.
A Stain Cleansed Battle: Choose your performing unbowed Magistrate, target an enemy card without attachments or an enemy unit, and pay Gold equal to the card or unit's total Gold Cost minus 2: Destroy it.
Wide Valley negates the destruction of a card... but not of a unit. Is there a Rulebook clarification of unit kill being multiple card destruction or is it labeled separately?
Wide Valley's trait will negate the destruction of each of the cards in the unit.
See Glossary, Unit: A cost or effect like “Destroy a unit” or “Bow a unit” is considered to be multiple separate costs or effects, each affecting one card in the unit (see Definition of effects). Costs and effects on a unit are applied to the Personality and all cards in the unit at the same time.