Primus is the kett second-in-command to the Archon and is trusted with leading many of the kett's most dangerous factions. She is a hands-on leader and orders from her are treated as coming from the Archon himself. Her main area of responsibility appears to be managing the exaltation and conquest of Heleus.
The Primus is believed to be extremely orthodox, ordering punishments for kett who deviate from social norms and traditions. She is also concerned over the missions to investigate Remnant technology since they interfere with military exercises and recon missions. While the Primus expressed her 'concerns' to the Archon about the latter's obsession with Remnant, she does not publicly share her dissent about the direction Archon took with the Heleus Cluster campaign. However, that hasn't stopped the Primus from gathering her own faction, spreading her side's propaganda against the Archon, even going as far as to solicit the Pathfinder in her attempts to engineer the Archon's downfall.
Pathfinder Ryder first encounters the schism on Elaaden, which, if the trail is followed, eventually leads to a vid-com with the Primus on Eos, where she reveals herself 'as a traitor' to the Archon. She believes that Archon's obsession with the Remnant derails their cause and incites chaos. Furthermore, she wants Archon gone, believing his quest for Meridian is for his own ambition. Through various audio logs, the Primus expressed that the kett could and would conquer the Heleus Cluster without the Remnant technology anyway, thus Archon's obsession with the Remnant technology could only mean that his ultimate goal is to turn against the Kett Empire for his own ends.
In the vid-com, the Primus proposes a deal: in exchange for killing the Archon, she'd provide Ryder the kill code for the Archon's ship, which during the final mission Ryder could use to drastically weaken the kett opposition encountered.
With or without taking up the deal, the Primus tells Ryder that they won't speak again.
After the Archon is killed, Primus becomes de facto leader of the kett in Heleus Cluster.