Under the leadership of former Senator Kev Rosse the Spirit Cats were one of the factions to break away from the Republic of the Sphere in the early 3130's following the widespread collapse of the HPG network. Most followers were later absorbed into Clan Nova Cat while others made a home for themselves on the world of Marik.
Galaxy Commander Kev Rosse is a Senator of the Republic of the Sphere, but in his heart he has always been a Nova Cat. As the interstellar silence fell, he declared that only one thing matters: the preservation of the Nova Cat. the Nova Cat Clan has always been capable of transforming itself to ensure survival, as when Rosse's ancestors joined the Republic, but Rosse actually wants to lead his local Clan members back to a "Purer" form of Cat.
Though torn by his loyalties to both The Republic and House Kurita, where the rest of the Nova Cats reside, he has announced that a vision has shown him that neither of those paths will allow his warriors to survive. Instead, they must separate themselves from what the Nova Cats have become, hence the Spirit Cats name, and draw closer to what the Nova Cats once were. He argues that this means making no alliances with or joining Inner Sphere governments.
Furthermore, his vision has shown him a place they must find to secure the survival and independence of his Clan. If that requires that he surrender all previous allegiances, then so be it. He is convinced that through his visions and leadership, he will guide the spirit cats down the path to survival.
 Actions in the Republic
In Febuary of 3134, Star Captain Cox Devalis led a Trinary of Spirit Cat warriors to Wyatt in search of sanctuary, only to engage in a running battle with the Republic Militia, Bannson's Raiders and the Oriente Protectorate's elite Eagle’s Talons battalion for control of the world. By the end of the series of battle, Cox was convinced that Wyatt was not world he was seeking.
A Trial of Annihilation against the Spirit Cats was announced by Mystic Kisho in December of 3136 after a number of mystics were murdered. Immediately thereafter, the Nova Cats attacked the Spirit Cats on Addicks. There, Kev Rosse fought Kisho and defeated him in battle, proving to his people that he was not responsible for the deaths of the mystics. However, as Rosse was speaking to Kisho after the battle, he was assassinated by an unknown party.
 Post Kev Rosse Era
After Galaxy Commander Kev Rosse was assassinated, Kisho took Rosse's vision as his own, and demonstrated his sincerity by absorbing the Trinary of warriors Rosse had with him, making each a bondsman before releasing them immediately into the Warrior Caste.
Prior to Rosse's death, Galaxy Commander Rosse had dispatched a Cluster-size task force to Prefecture VII to seek out a sanctuary for rest of the Spirit Cats. The task force, lead by Star Colonel Rikkard, invaded the world of Marik by October 3136 to see if it was their sanctuary. There, they engaged Marik-Stewart Commonwealth forces defending the planet in a nine month campaign. When the Commonwealth led the Spirit Cat forces into the metropolis of Dormouth late in the campaign, the fighting really got bogged down.
In February, 3137, Rikkard learned of Rosse's assassination, and immediately realized that no reinforcements from his Clan would be able to come to his aide. It was then Lady Julietta Marik convinced Rikkard to join in a alliance with the Oriente Protectorate against the Commonwealth forces, rather than returning to the rest of the Nova Cats.
As the Spirit Cats continued their battle, the alliance quickly proved to be only a mutual understanding and not immediate military intervention. Rikkard then decided that the alliance, with so few Clan Warriors remaining, was not enough to ensure their survival, and therefore contacted Clan Sea Fox for military aid in exchange for trade items. With the Sea Fox forces on hand, the Spirit Cats defeated the last Commonwealth forces by June, securing Marik as a sanctuary for both the Spirit Cats and Sea Foxes alike.
After being grievously wounded by an assassination attempt, Rikkard had Julietta retrieved from Oriente so she could be on-planet for rehab. She later joins the Spirit Cats as their political guide.
In June of 3138, Captain-General Jessica Marik requested the Sea Foxes and Spirit Cats garrison Abadan and Avellaneda. Lady Julietta decides to lead the Clan forces, and convinces nearby worlds into forming the Clan Protectorate, with the Spirit Cats and Sea Foxes being mutual partners in administrating and protecting the people of those worlds.
In February of 3139, Jessica Marik asked the Clan Protectorate to help take Atreus from the Regulan Fiefs. The Protectorate accepted, and in April they joined the invasion of Atreus in Operation Homecoming, and secured the world for the formation of a new Free Worlds League.
As part of the Clan Protectorate, the conclave of Spirit Cats and Sea Foxes are given a voice in the newly formed Free Worlds League.