Does Mask of Foresight retroactively stop applying if the attacking/defending unit is no longer alone during the reaction window in a showdown?

Ruling: No, Mask of Foresight does not retroactively stop applying. Once the "when I attack or defend alone" condition triggers and the triggered effect is applied, it is no longer affected by whether the unit remains alone.

Nuances:

• "When" creates a trigger that goes on the stack, so the condition only needs to be true at the moment of triggering
• This differs from passive abilities that evaluate their conditions almost constantly