The Dragoon is a mechanical warrior that can fight both ground and air units.
Veteran Protoss warriors who have been crippled or mortally wounded in combat can volunteer to continue their service to the Conclave by being transplanted into Dragoon exoskeletons. Within a short time, the fallen warriors learn to control the movements of the large, mechanical walker as naturally as if they were within their former bodies. Dragoons provide essential supporting fire for the Zealot legions by launching bolts of anti-particles sheathed in a psychically charged field. These disintegration bolts are effective against both air and ground targets.
Dragoon is no more in StarCraft 2. The unit that took his place is the Dark Templar Stalker.