The Valkyrie is a heavily armored, air-to-air frigate that can unleash devsatating damage upon clusters of units, such as Mutalisks and Overlords.
The Valkyrie employs an air-to-air attack that issues a volley of 8 small missiles at it's target. The missiles impact not only their target, but also damage any enemy units within a 3 x 3 matrix area. Each missile does a small amount of splash damage in this target area.
The Valkyrie Frigates are a powerful addition to the UED's Expeditionary Fleet. The Valkyries' H.A.L.O. missiles are capable of reducing most conventional star fighters and airborne structures to rubble. The missiles are fired in volleys of eight, and impact within a large area of effect. The dispersal radius of its targeting system is designed to achieve maximum damage to not only its intended target, but also adjacent targets within the blast area. Valkyries are heavily armored, and can take substantial punishment from enemy fire before they suffer any core system failures.
The Valkyrie was introduced in the Brood War expansion pack, when all three races' air fleets were bulked up with air-to-air fighters. All three of these units (including the Corsair and Devourer) have been scrapped from Starcraft 2.