After the Beast Heavy Cruiser tries to infect the Bentusi Exchange, it self-destructs rather than be taken over. The blast destroys much of the Beast forces and severely damages the Beast cruiser and the Caal-Shto, leaving the carrier without navigational systems.
The Kuun-Lan assists it through the Kadiir Nebula, past a heavily defended imperialist Taiidan research base. The Kuun-Lan and the Caal-Shto make it though the nebula to a slipgate, and the Caal-Shto promises to bring in the warrior kiithid to "mop up this infestation".
Later, the Kuun-Lan is under attack by Imperial Taiidan forces called in by the Turanic Raiders after the Kuun-Lan salvaged the Siege Cannon that they were after. In the thick of battle, the Kuun-Lan detects the Caal-Shto's hyperspace signature in an asteroid pocket far from the fighting. The Caal-Shto requests them to "come to us". When Somtaaw Fleet Intelligence warns the Caal-Shto that the Turanic Raiders have changed course to intercept it, it replies "They come. Good." When the Raiders arrive, the Somtaaw realize that the Caal-Shto had been subverted by the Beast. Shortly after, the reformed engine section of the Kuun-Lan, now forming a Beast Mothership jumps in.
The ultimate fate of the Caal-Shto is not clear, but likely it found its end at the hands of the Hiigaran warrior Kiithid after the destruction of the Naggarok and its other 'children'.