The motherships were around ten-times larger than a Federation Constitution-class starship, and possessed weapons technology that outmatched Federation technology in the mid-23rd century, including a type of muon weapon which took a huge amount of energy to fire. The motherships could also deploy a series of satellites, would basically served as orbital weapon platforms, in orbit of a planet, which could serve independently, or be controlled by the mothership.
In 2257, the USS Constitution engaged a mothership that was attempting to subjugate the Federation member planet, Sordinia IV. Over the next eight years, additional motherships were encountered by the Federation starships USS Excalibur, USS Lexington, USS Potemkin and USS Defiant in orbit of various planets, including Velarrh VII, Mos'rammi IX, Indish III, Linyar II and Tenekratus IV. (TOS - My Brother's Keeper novel: Constitution)