Clotho is one of the three "Biological CPUs" assigned to operate one of the Earth Alliance's new Gundam mobile suits, GAT-X370 Raider. As with his comrades, his personal data has been erased from the military's records.
The talkative, quarrelsome Clotho is constantly arguing with his teammates, and he likes to shout out video game-inspired battle cries as he fights in his Raider Gundam. Between missions he spends his time perfecting his shooting skills on a portable game system. When in combat, Clotho seems rather psychotic, but mostly very proud. He is extremely upset when the Calamity jumps on his Raider in order to get back to their ship and shows extreme anger at the near misses the Calamity's weapons seem to throw his way. In his final moments, he seems to be suffering from withdrawal in his last attack on the Duel and Buster, showing a complete lack of restraint or self-preservation.
First Alliance-PLANT War:
He and his teammates, Orga Sabnak and Shani Andras, would be first deployed to attack the neutral Orb Union. Prior to heading out, his team was prompted by Muruta Azrael, their superior and defacto leader of the Earth Forces, to avoid damaging the Mass Driver and Morgenroete. First, he and Orga would together target the Atlantic Federation's defected Archangel, only to miss. After Orga disembark Clotho's Raider and goes on his own, the latter would attempted his own second attack on the rogue Earth Forces ship, only to get intercepted by and then shift his focus to Kira and his Freedom Gundam. He and Shani would together engage Kira, albeit at the same time unable to cooperate by some amount. Unbeknownst to the Clotho, Athrun was also watching from the side, and intervenes right when the former was about to deliver the potentially final blow to Kira. Definitely wasn't expecting this, Clotho gets annoyed by Athrun's intervention, and proceeds to take out both Kira and Athrun. The three Biological CPUs engage the duo for some time, all the while even at some points friendly firing at each other out of annoyance. Eventually, the time of their performance enhancing drugs run out and they fall back, suffering from withdrawal. Because of their failure, Muruta had his underlings who worked with the Biological CPUs let the three suffer as punishment before they recieved another dose.
In the second round, the trio would engage Kira again. He would be overwhelmed until Athrun's arrival. Even this time and with more enhancements, the trio are still having difficulty. When Orga's Calamity runs out of power, Clotho insults Orga, telling him to leave if he wants and that he was on his own. When Athrun slices the Raider's mace, Clotho would try to return, and Orga would then return the favor by insulting him back and boarding the Raider when it was in its Mobile Armor form, much to Clotho's annoyance at Orga not asking first.
Because of their failure for the second time, they were given the same punishment. By the time they come back again, the Archangel and Orb have already gotten their secret plan started. Kira and Athrun briefly hold off the trio before clinging onto the Kusanagi and fire one last shot before making their escape. The trio would witness the self-destruction of Orb's Mass Driver.
The Battle of Mendel Colony
The Battle of Boaz / Operation Peacemaker
Clotho and his team would participate in the attack on ZAFT's space fortress Boaz. When the Peacemaker Force proceeds, he and his team cover them and ward off the ZAFT defenders, until the nuclear missiles destroy the base. He also enjoys the sight of the explosions.
After Boaz's destruction, the trio move on to aid in the destruction of the PLANTs. He takes out some units and then engages Yzak Joule and his Duel Gundam, while the other two take out members of the Joule Team trying to stop the missile carrying Moebiuses.
Enraged at the attempt at their homeland, ZAFT returns fire with GENESIS , which Clotho and his team would witness in shock.
Second Battle of Jachin Due
His death is portrayed differently in the TV series/HD Remaster and the Special Edition.
In the TV series/HD Remaster, after the death of the two other Biological CPUs, Shani Andras and Orga Sabnak, Clotho's mental stability begins to deteriorate and he feels the pain/loss, and even though Raider's power was almost depleted, he continues to battle. He attacked Yzak in his Duel and the injured Dearka in his damaged Buster. While Yzak was trying to counterattack with Duel's beam rifle, Clotho destroys it. He would keep pressing the assault on Yzak, pushing both himself and his Raider to the very limit. Yzak then used the Buster's rifle to replace the destroyed beam rifle, while Clotho charges the Raider's "Zorn" 100mm energy cannon. Both pilots fire at each other simultaneously; Clotho's shot only caused minor damage to the Duel, but Yzak's shot would hit its target, destroying the Raider and killing Clotho in the process.
In the Special Edition, Clotho is killed by Buster/Dearka immediately after Orga's death.
Second Alliance-PLANT War:
While he does not make an appearance, his remaining data file does show up in the ruined Lodonia Lab.