The Viper is a new strain of Zerg fliers incorporated into the Swarm to enhance their scouting and reconnaissance abilities.
Ocular Parasite: The Viper grants detection to an allied non-massive unit. The Viper can target other Vipers or itself with this ability. It can only be used once in a long while.
Consume: The Viper consumes a biological creature or structure slowly to gain back 50 energy.
Blinding Cloud: The Viper spits a green cloud. Ranged units in the cloud have their ranged reduced to one. Units can move out of the cloud to fire normally.
In the game series, the Viper is a concept idea for a new strain of Zerg aerial support unit.
For more information see the Viper on the parent site.