When the user takes damage and crosses the threshold to meet the @Trait[desperation-1-3] Condition from that damage, they may spend @PP[-3] as a Free Action @Trait[interrupt] to gain @Tick[4 shield].
Trigger: The user takes damage and crosses the threshold to meet the @Trait[desperation-1-3] Condition.
Effect: The user gains @Tick[4 shield].