Around 21 BBY, Tamson was sent as an envoy to the system, which was slowly falling to an advance by the Confederate Navy. There, he secretly assassinated King Yos Kolina of Mon Calamari and the subsequent Mon Calamari, causing Quarren tensions to rise in the Calamari system. The Galactic Republic responded by sending Jedi General Anakin Skywalker and Senator Padmé Amidala in an attempt to quell the tensions. But Tamson led a pre-emptive strike against the Mon Cals, and personally went after Prince Lee-Char, though the attack was temporarily driven off by Republic reinforcements. Tamson soon brought in Hydroid Medusa into the battle, driving the Republic forces deep into the underwater caves. He then turned to his Quarren allies, angry that they chose not to join the battle during his second strike. He personally warned the Nossor Ri not to disobey Count Dooku's orders again, otherwise he'd kill him on the spot.
As Tamson's forces gained control of the Calamari cities, Dooku ordered him to locate and kill the prince, so as to crush the morale of the Mon Cals. Tamson predicted that his quarry would attempt to reach the waiting Consular-class cruiser on the surface and had it destroyed just before they could reach it. He later received word that the long-ranged sensors had been destroyed, rendering the Separatists blind if any Republic reinforcements intend to arrive and rightly so, as Gungans are deployed from a Republic cruiser.
When Tamson was informed that the prince was spotted attempting to rally the hopes of his people, he decided to hunt the prince down personally. He deployed Trident-class assault ships to create whirlpools in order to confuse his enemies. Tamson then attempted to kill Lee-Char, but Jedi Kit Fisto and Ahsoka Tano stood in his defense. Eventually, Tamson had all the Jedi excluding Tano and Senators Amidala and Meena Tills captured, though the prince still eluded him.
Tamson attempted to kill Lee-Char as he killed Yos Kolina. After killing off many of Lee-Char's soldiers Tamson attempted to fight off Char head-on and Lee took one of his explosive knives Tamson wielded and threw it into his arm. Tamson swam towards the Prince in an attempt to kill him, but Lee-Char managed to destroy the bomb and Tamson before he got too close.
Personality and traits
- "There's plenty of suffering to go around."
- ―Riff Tamson reveals his sadistic nature
An ambitious warlord, Tamson acted as an envoy for the Separatists on the aquatic planet Dac, perturbing political stability between the native Quarren and the Mon Calamari following the assassination of King Yos Kolina, an assassination that he had been personally responsible for. He was extremely vicious, mercilessly killing anyone who got in his way and was not above threatening his allies when he was enraged or frustrated. Tamson was loyal to Count Dooku and never disobeyed his orders and would threaten anyone who even considered disobeying the Sith Lord. He was also sadistic and enjoyed watching his prisoners suffer, commenting that whether the Jedi told him the whereabouts of Lee-Char or not, he would torture them either way.
Skills and abilities
Riff Tamson was shown to be a deadly opponent in battle, even managing to defeat Jedi Master Kit Fisto in hand to hand combat. He appeared to have a preference for hand to hand combat normally attacking his opponents with his powerful jaws or his bare hands but also used explosive knives when he attempted to kill Prince Lee-Char. Ironically it was one of his own knives that was responsible for his demise.
In addition to being a formidable warrior, Tamson was a skilled commander and strategist and was well suited to underwater warfare. Tamson was also a very powerful swimmer, being able to match a Republic OMS Devilfish sub in speed underwater. 
Behind the scenes
Tamson's manner of death is similar to that of the shark in Jaws where police chief Brody shot the gasoline barrel attached to the shark's mouth as it charges towards Brody, similar to how Lee-Char shot the bomb attached to Tamson.
- Star Wars: Clone Wars Adventures – "Mission on Iceberg Three" (First mentioned)
- Star Wars: The Clone Wars – "Water War" (First appearance)
- Star Wars: The Clone Wars – "Gungan Attack"
- Star Wars: The Clone Wars – "Prisoners"