A Grunthor was a huge carnivorous land based Basilisk Leviathan relative native to planet Sargasso. Each contained a Leviathan Soul and raritanium. They attacked by shooting fireballs from their mouths, jabbing with their tusks, or by stomping their feet if their prey got too close. With their powerful attacks, anyone unlucky enough to disturb them had to stay light on his feet to avoid the possibility of rapid death. In addition, their saliva was one of the most corrosive substances in the Polaris galaxy.
There are 16 Grunthors on planet Sargasso.
- The skill point Extinction could be acquired by killing all of the Grunthors on planet Sargasso.
- Being highly corrosive, Grunthor saliva was used in the Toxic Upgrade for the Constructo Bomb.
- It was said that War Groks ate Grunthors. 
- Ratchet & Clank Future: Tools of Destruction (first appearance)