4 Mask is a Rahkshi of Xenon in the TBTTRAH Series. His home location is unknown, but what is known is that he takes a certain delight in watching the house residents suffer. He was once a well-standing inhabitant of the house, but after a failed attempt to take it over, he was kicked out. After several attempts to destroy the house, he was confronted on board a space station by MT and 5 Mask, and "killed" when the space station was destroyed.
However, he returned nearly 2 years later, in what was dubbed as a: "ridiculous spin off of Attack of the Clones." 4 Mask, with the help of some nifty teleportation, managed to sneak into the Coffee Mines in the house. There, he found DNA strands of many of the deceased house residents, and then took those strands back to his base on the planet Vundas. However, unbeknowest to him, the clones did not maintain their intelligence, and went beserk.
In the midst of all this, 4 Mask was assigned by the Dark Lord to raid a IUPD planet. He did successfully, but was encountered by MT and Kopeke. After a quick skirmish, 4 Mask managed to chase the two Toa off and eventually bomb the rest of the city. 4 Mask returned to Vundas, and, after finding his base of operations discovered by yet more Zehvor, decided to hightail it out of there, kidnapping Mesonak and Sonu. The kidnapping backfired, however, as Mesonak managed to free Sonu, and then Sonu sliced off 4 Mask's left arm.
4 Mask later attacked the planet Vundas and captured it, sucking in to the Second Dimension with the help of an ark. He attempted to capture a group of Matoran leaders, but was blocked by Toa Vecolity until the Matoran could escape. In revenge, 4 Mask enslaved Vecolity, and brought him to his new base of operations.
4 Mask was later encountered by MT in the middle of the planet Kyrell. In a furious attempt to kill the Toa, he went bezerk and supercharged himself with Xenon, deciding that he was willing to kill himself in order to finally kill a Zehvor. Ironically enough, MT then went on to kill him with his own Xenon missile.