Dr. Thaddius Blakk is the main antagonist of Slugterra, and the owner of Blakk Industries.
The owner of the powerful Blakk Industries, Dr. Blakk's business dealings have made him a rich and powerful man. Ultimately, his business is hiding his true purpose: to control all of Slugterra and destroy the magical slug energy that protects this underground world. A powerful slugslinger with a terrifying multi-shot Harbinger Firestorm blaster, Blakk has corrupted his slugs through the dark science of ghouling, turning them into ruthless shadows of their former sluggy selves.
Thaddius 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. After his encounter with the Unbeatable Master, he returned to take the cavern for his own. This lead to his first encounter with 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 Darkbane. As shown in "Back to Blakk", the first ghoul was a Greneater. Following those events, Blakk used a Tempesto to defeat Will Shane.
Slugterra: Return of the Elementals
After being sucked in a terraportal to the Deep Caverns. He returned in Return of the Elementals in a mutated form and he is working with the Goon and later controlled by the Goon to capture and ghoul the Elemental Slugs, but failed and along with the Goon was trapped in the Deep Caverns by Will Shane.
- Blakk only beat Will Shane in a duel once.
- Blakk can carry a Gattler while others have to mount it onto a cart, hinting that he is strong.
- Blakk fears a Fusion Shot, as seen in "The Return".
- Although he fears fusion shots it is seen in "The Unbeatable Master" that even they do limited damage to him.
- The 'V'-shaped insignia that Blakk wears originally came from Viggo Dare, a symbol worn by his gang members.
- Blakk's skin was originally tan (as an adult) but turned pale due to a Deep Cavern portal.
- In The World Beneath Our Feet Part 1 we can see a Flopper in Blakk's bandoleer.
- In his new form his left hand has four fingers.
- After his trip to The Deep Caverns, he turned into a monster, similar to after The Emperor fell into Dark Water.
- In his new form, he can ghoul slugs, without the need of machines, just like The Emperor after falling into Dark Water.
- In Back to Blakk he appears interested in the Shanes' secret about the Burning World, as if he suspected that it is more than a legend, but Eli refuses to reveal his secret. However, in Into the Shadows his son Tad comes to Slugterra from the Surface and already knows about his father's enterprise and Ghouling. So Blakk's knowledge about Surface is still unclear.