There have been a multitude of villains in the TBTTRAH series. Some of the most famous are below:
The "original" TBTTRAH villain. He first appeared around chapter 40 of TBTTRAH, and has not stopped causing trouble since. Originally a good guy, this Rahkshi of Xenon quickly fell under the influence of the Dark Lord and attempted multiple times to take over the house since. He was "killed" by MT and 5 Mask, but showed up again just the same, and is now attempting to use cloning to create an army of dead house inhabitants.
Mete, more commonly known as "Omega Mete," was a Toa created out of a pool of Anti Xenon, also known as Cherry Slushie. Upon his creation, he quickly dismantled Omega Turtle and nearly killed MT had it not been for a well timed "bring the ceiling down" maneuver by the Zehvor leader. Mete later used Xenon to corrupt the minds of the government and got them to destroy the house. He was later defeated by a team of MT, Omega Turtle, and Vecolity.
A new Mete was created from Mete's DNA by 4 Mask. This clone was the first one to successfully retain the memory of the deceased original, and this showed in a big way when the clone ran into a team of MT, Brenmac, Shadrahk, and Kopeke. The cloned Mete, with some ridiculous added strength, quickly dismantled the team and would have killed all 4 of the Zehvor had it not been for a cloned army of Vecolity-s. Mete was knocked unconscious, but managed to escape before everything on the planet surface was destroyed by a Terna bombing run.
Mete escaped to the floating plain of Tagan, where he met MT and Brenmac once again. He decided to stalk Brenmac and trapped him in a large circular room, where he found a pool of Xenon that quickly transformed him into Omega Mete. Omega Mete began to attack Brenmac when MT showed up again. Seeing one of the ones that was responsible for his defeat, Omega Mete attacked Brenmac and MT, but oddly enough was defeated resoundingly despite his Xenon infused status. After being badly beaten, he ran away to 4 Mask's space station. He was betrayed and killed by Sboog later.