Null Guardians

The Null Guardians are winged creatures that are native to the Null Void. They have no eyes, legs, or arms, and instead they have tendrills coming from their lower body which they use as limbs. They look somewhat like Vulpimancers (Wildmutt's species) with tentacles hanging from the undersides and wings. They are also capable of firing red lasers from their mouth. Their DNA is not in the Codon Stream as they are non-sapient and don't have DNA. They first appeared in the original series in the episode Truth, when the Null Void Projector was accidentally activated after Gwen tried to get hold of the projector from Phil. They appeared again in Back With a Vengeance when they attacked Kevin and Vilgax in the Null Void, but Vilgax manages to take control of the leader of the pack and uses the Null Guardians along with Kevin against Ben.

History
Their history is further explained in 'Ben 10: Alien Force' episode Voided. Doctor Animo, using his power to control animals, takes control of the Null Guardians as a personal army. It is also revealed that the Galvans created the Null Void as a prison for their criminals, as well as a place where aliens could settle and created the Null Guardians to protect theses peaceful aliens from the criminals, in a way the Null Guardians could be considered prison warden's of the Null Void. This explains why they mainly attacked Vilgax and Kevin in Back With a Vengeance, as they were the aggressors. Ben eventually defeat's Animo and frees the Null Guardians from his control. Though typically attacking Ben, the Null Guardians aren't normally hostile to peaceful creatures as their primary function is to protect the Null Void's settlers from the inmates.

Max had also been able to tame and ride one by the time he reappeared in War of the Worlds.

Null Guardians can be used to ride and can be easily tamed.

Original Series

 * Truth
 * Back With a Vengeance

Alien Force

 * Voided
 * War of the Worlds:Part 1
 * Vendetta

Ultimate Alien

 * Nor Iron Bars a Cage

Video Games

 * Ben 10 Alien Force The Video Game(only for DS) as a Null Void Guardian DNAlien. Levels: Warehouse, Cave, Tower.
 * Ben 10 Alien Force: Vilgax Attacks (Only for DS) Levels: Bellwood, Null Void, Bellwood Revisted.
 * Ben 10 Ultimate Alien: Cosmic Destructuion (Only for DS) Levels: Paris, Venezuela.

Other
The null guardians appear in Fusionfall in the null void levels.