Acronix went 40 years into the future and Krux escaped and lived in Ninjago City using the name Dr. Saunders, awaiting his brother's arrival. In their reunion, Krux hugged him for the first time in decades and started making plans to get revenge and conquer Ninjago. The twins were a good team, in spite of their opposing views such as technology and other matters. Nonetheless they still cared for each other, as they were quick to save the other when they were overwhelmed and were nearly successful in killing the ninja but Wu intervened.
They are currently trapped together in the vortex because of Wu.
Wu and Garmadon
Once good allies in the Serpentine War however, they became enemies after the twins sought to take over Ninjago. Krux and his brother fought Wu and Garmadon but the two stole their enemies' powers, which they trapped in the blades and threw them in a Temporal Vortex. Wu and Garmadon watched as their foes went after them but he saw they'd return.
Forty years later, Krux had went into hiding under Wu's nose and awaited the moment where his brother would return. He despises both Wu and his brother for their actions though never saw Garmadon again because of his death (coincidentally Garmadon was resurrected after the Twins' defeat). Krux's grudge to the brothers extends to anyone related to them, as he detested Lloyd for being Garmadon's son and Wu's nephew.
The Time Twins later abducted Wu and used him as leverage against Kai and Nya, while they mocked his situation even after the Ninja complied they had refused to cure him after what he and his brother put them through as a final revenge. After being cured by his students, Wu got his revenge on the twins by confronting them with his students. The twins were greatly shocked by his return and fought him again. When Wu saw the aftermath of the villains' actions on his friend Ray and nearly watched them kill Kai and Nya, he decided to finally put an end to them by sabotaging the Iron Doom and choosing to stay behind to finally end their conflict. Krux and his brother fought Wu for the last time and were presumably defeated by him, avenging the actions done onto him and his friends by their hands. Wu also had qualms in leaving the Time Twins behind in the vortex and they are currently still lost in time.
The Elemental Alliance was a group of Elemental Masters during the serpentine wars. The Time Twins fought alongside the alliance during the war, but rebelled believing they could conquer Ninjago since they had the most powerful element.
He was responsible for the disappearance of Kai and Nya's parents after threatening their safety when they were. He later threaten the parents of the ninja along with Wu unless they got the last time blade. The siblings struck back with help from the rejuvenated master and foiled the time twin's plans. Krux and his brother fought the two and overpowered them, they would of finished them had Wu not intervened.
The other Ninja were shocked that Dr. Saunders was really Krux, a mad villain and sought to stop his plans. They barely defeated the Time twins at the end of Season 7.