Primus

Primus' existence was first hinted in Ghost Town when Vilgax freed Zs'Skayr in exchange for a secret about the Omnitrix. This secret was later revealed to be the existence and location of Primus in the eponymous episode, where Primus appeared. Intending to disable the Omnitrix and take it from Ben, Vilgax went to Primus. Sensing his arrival, Primus called Azmuth and the Omnitrix. The Omnitrix left Ben to Azmuth to help him defeat Vilgax. Vilgax eventually defeated Azmuth and took the Omnitrix but was unable to use it. Upon learning how important Primus was for Azmuth, he threatened to destroy it, but Ben was able to trick him in order to take the Omnitrix from him and defeat him. After Vilgax was gone, Azmuth moved the location of Primus so Vilgax could not find it again.