Mori's rank was never stated but Servalan promised to make him her Supreme Commander should he succeed in his mission. She may even have meant it.
Mori and his squad made contact with Bershar on Obsidian and were given teleport bracelets the Pyroans had taken from Tarrant and Dayna. He was able to trick Vila into teleporting them on board the Liberator where they attempted to take the ship intact.
They were unable to stop Avon from ordering Zen to operate the weapon systems, and the ship came under heavy fire. In the confusion Avon shot and killed two of the squad before being wounded and knocked out by Mori. Fearing the Liberator would be destroyed in the battle, Mori and his last surviving trooper withdrew to the planet's surface taking Orac and Cally with them.
Orac supplied Mori with an approach course for the planet which would avoid the Pyroan detectors, which he passed on to Servalan. He then laid an ambush for Tarrant and Dayna, but they were warned telepathically by Cally. Dayna threw a grenade which killed the trooper outright, the blast knocking Mori into the crater of Obsidian's volcano. He fell into the lava and was killed.
Mori was ambitious and resourceful, recognising the strategic value of Orac and coming very close to taking the Liberator without firing a shot. He was not quite as ruthless as Servalan and initially quailed at executing the Pyroans Milus and Natin (his qualms soon passed however). He also had to be stopped from killing Dayna and Tarrant by Bershar.