Dr. Thaddius Blakk is the main antagonist of Slugterra. He is the owner of Blakk Industries.
Thaddeus Blakk grew up dreaming of becoming the top Slugslinger around. He was also a candidate for becoming a student of the Unbeatable Master but he lost to Will Shane. He would do anything to win, even cheat. This didn't sit well with his chief rival, Will Shane. After he defeated Will Shane, Blakk retired from Slugslinging uncontested and turned his interests to science and industry. Blakk took a broken-down train system and turned it into the SlugTerran Express, a system of high-tech, high-speed trains that connect all but the most remote caverns. Despite his success and wealth, Blakk remained unsatisfied. Now, he will settle for nothing less than total domination of all SlugTerra.
In "Back to Blakk" he reveals his life's story, beginning with when his father abandoned him, causing Blakk to grow up in a lawless cavern run by the gangster, Viggo Dare. After his encounter with the Unbeatable Master and Will Shane, he returned to take the cavern for his own from Viggo Dare. This lead to his second encounter with the new Shane of SlugTerra: Will Shane, as well as Blakk's discovery of dark water. After some experiments, he was taken to the Deep Caverns causing his skin to become white and leading to his alliance with the Dark Bane. As shown in "Back to Blakk", the first ghoul was a Greneater. Following those events, Blakk used a Tempesto to defeat Will Shane.