The Empress class carrier was the paramount of carrier designs in the core- as it was the only 'supercarrier' in existence at the time. Though the design has it's origins in Asshur, several other countries operate them, and a few construct them under license. Because of their prominence in the affairs of the core, they've become a standard by which other warships were compared. In fact, because of their size and capability they are considered to be the only core-constructed example of a mass-produced mothership design- matched only by the Vaygr starships in the deep east.
By fifteen years after the Taiidani return to Hiigara, only thirty seven of these massive starships were being operated and many of them out of the Frerrn aggregate. Some predicted that this meant the Frerrn were preparing for an eventual war with the Kushan Empire, but thsi was forestalled when the empire collapsed from within. Instead, the Frerrn launched an invasion of the core some years later with their Empresses leading battle groups.
The Frerrn themselves have a high preference for plasma technology- despite how easy plasma bombs are to shoot down by lasers, and despite the long load times and cost to utilize the weapon. They are one of the only races in the core to employ plasma weapons as heavy weapons- constructing "Plasma Mortars" to lob oversized plasma bombs into enemy targets. While it's debatable if plasma weapons are a superior choice over ions, the Frerrn continue to place plasma weapons in high reguard over other direct-energy weapons systems.