The Rutan's developed motherships as part of the their spacecraft fleets. They had crystalline structures and anti-gravity systems. In the 1900s, after deploying a scout to the island, a Rutan mothership descended on Fang Rock to "blast" it into "molten rock".
The Fourth Doctor, acting on Leela's suggestion, fitted Fang Rock lighthouse with a carbon oscillator, a powerful laser, which destroyed the mothership as it had lowered its shields to conserve energy, not expecting to be threatened by local technology. (TV: Horror of Fang Rock)
Their appearance could be disguised by chameleonic technology mapping its coordinates on the outer dimensions of the surrounding area. (AUDIO: Castle of Fear) Motherships were powered by warp core engines. (AUDIO: The Eternal Summer)