Null Guardians

The Null Guardians are winged creatures that are native to the Null Void. They have no eyes, legs, or arms, instead having tendrills coming from their lower body for use as limbs. They first appeared in the original series when one was released by Max's former partner to attack Ben as Grey Matter, who was able to gain control of it. 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.

Their history is further explained in '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.