Plumbers (BTR)

The Plumbers are a secret intergalactic military led by Azmuth and the Galvans. Their primary Earth base is under Fort Soledad near Bellwood.

Background
They were created by Azmuth hundreds of years ago, with as much of an intention of protecting the work-in-progress Omnitrix as protecting the universe. They have been in operation this entire time since.

Role in the series
You could consider their first "appearance" to be at the very end of "The Paradox," tazing the gang, though they were not actually explained until the [[Secrets (BTR)|next episode, in which it is revealed that Azmuth was behind this, demanding the Omnitrix back because Max had no right to give Ben the Omnitrix. However, by the end of the episode, Azmuth saw Ben stop Vilgax's main plan, and let him keep it, at least until they could stop Vilgax for good.