He was voiced by Michael Daingerfield.
Long ago, Acronix and Krux were the Elemental Masters of Time in Serpentine Wars time. When the war ends Acronix and Krux betray Wu, Garmadon and the other Elemental Masters, because they liked their own Elemental Power as a valuable weapon. Later Ray and Maya made the four Time Blades from Chrono Steel, the purpose of export Acronix and Krux's powers. When their powers were exported Wu and Garmadon made the Time Vortex where the Time Blades was destroyed. Acronix and Krux attacked after the Blades and there was thought to have disappeared into the time, later it became clear that before Acronix disappeared was a visible sign that told when he would return, it was forty years and Wu saw it. But Wu did not know that Krux saw the sign to, but he had not been in the Vortex. Krux was able to plan, he always traveled in disguise and decided to use eggs of the Great Devourer to create his own army. The warriors needed the armors, the weapons and the vehicles, and Krux knew who could design them. Krux presented himself as a kind Dr. Sander Saunders and he received Ray and Maya to trust him, they thought he was their friend until he deceived them. He told his brother's return to the present and he forced them to design armor to plot revenge for the fact that they made the Time Blades. And if they had not agreed to the plot then Krux threatened Kai and Nya. When Acronix returned they ordered the Vermillion Warriors to take the hand-literate builders and the metal. Their plan was to build the Iron Doom spitefully manage all the time. Krux hated modern technology, although he said that the technology can help.
When he and Acronix were going too far into the future, Kai, Nya and Wu met them on the way in time. When Wu saw Ray he untied the Return Blade and threw it with Kai and Nya. Wu remained to Iron Doom and he, Acronix and Krux disappeared in time.
Krux and his brother continued to battle their enemy before they were presumably defeated by him. It can be assumed he and his brother are still lost while Wu managed to escape the vortex though he was de-aged into an infant.