Winter's Veil is a tier 5 skill in Aurelia's Cold Money skill tree. This skill allows Aurelia to emit a Cryo nova every time she is struck by a melee attack, or when her shield is depleted.
Cryo Nova Damage
Aurelia's shield needs to fully recharge in order for her to emit a nova next time the shield becomes depleted. On the other hand, every melee attack will trigger a nova, regardless of Aurelia's current shield points.