Does Unyielding Spirit negate Vi's might increase or remove cleave effects?

Question

Accepted Answer

No. Unyielding Spirit does not remove or negate Might increases or granted keywords from Cleave. It only prevents damage that would be dealt by spells and abilities; it does not undo buffs or remove granted abilities, nor does it prevent normal combat damage from units whose Might was increased.

Unyielding Spirit prevents spell and ability damage, but it does not remove the +3 Might or the granted Assault from Cleave, and it does not undo other Might changes. If a spell or ability would deal damage (for example, Alpha Strike dealing damage equal to a unit's Might), that damage is prevented by Unyielding Spirit. Regular combat damage assigned and dealt during a Showdown is not 'spell or ability' damage and is not prevented by Unyielding Spirit.

You play Cleave: it grants a unit Assault 3 this turn and the parenthetical +3 Might while it's an attacker; the unit's Might changes immediately as the spell resolves and is evaluated as current Might [710]. If an effect would deal spell or ability damage (for example, a damage-dealing spell like Alpha Strike), that damage is prevented by Unyielding Spirit if it is active because Unyielding Spirit's text is "Prevent all spell and ability damage this turn." The prevented damage is not marked on units [143.3.a]. If the increased Might from Cleave causes a unit to deal more combat damage during a Showdown, that combat damage is not spell or ability damage. Combat damage is assigned and dealt as part of the Combat Damage Step and is not the same as 'spell or ability' damage, so Unyielding Spirit does not prevent it [460.2.c.1]. Because Unyielding Spirit only prevents damage, it does not remove keywords or buffs granted by spells or abilities (such as Assault or temporary Might increases); those effects remain until their normal duration ends [710].

If a spell that both grants Might and immediately deals spell damage is played (not the case for Cleave as printed), Unyielding Spirit would only prevent the damage portion — it would not strip the Might buff unless the spell's text specifically says to remove it. The rules treat damage prevention separately from modifying Might [143.3.a] [710]. If a unit's Might is referenced later by a spell that resolves after Unyielding Spirit is played (for example, you grant +Might then an ability deals damage based on current Might), Unyielding Spirit will prevent that spell/ability damage, but the Might value used for other non-damage effects remains changed until the effect expires [710] [143.3.a]. If a target of a damage-dealing spell changes zone off the board (becoming a non-board object) while the spell is on the chain, that target's information (including Might) becomes null per targeting rules; preventing damage via Unyielding Spirit is distinct from that situation [359.3.e.12].

The key point is that Unyielding Spirit's text—"Prevent all spell and ability damage this turn."—only affects damage that originates from spells or abilities. Granting Cleave (an [Action]) gives a unit Assault 3 and the parenthetical +3 Might while it's an attacker; that is a buff that changes the unit's current Might as it resolves and is tracked as a non-damage effect [710]. Preventing damage does not remove buffs or keywords. If the increased Might from Cleave causes a unit to deal more normal combat damage during a Showdown, that combat damage is not 'spell or ability' damage and thus is not prevented by Unyielding Spirit—combat damage is its own process (assigning damage is not the same as dealing spell/ability damage) [460.2.c.1]. Conversely, if an actual spell or ability attempts to deal damage (for example, Alpha Strike, which is a spell that deals damage equal to a unit's Might), that spell/ability damage would be prevented by Unyielding Spirit and the prevented damage would not be marked on units [143.3.a]. Therefore, Unyielding Spirit does not negate or remove the Might increase or the Assault effect from Cleave; it only blocks damage from spells and abilities.