The massive dynatrope next to Gond dwellings.
Dynatropes were machine spacecraft used by the Krotons. They had crystalline structures, being composed of 80% tellurium and being "grown," using massive root-like structures to stabelise the ship. They were equipped with disintegrators, and were powered by mental energy, one Dynatrope requiring four "high brains" to operate it.
One Dynatrope crash-landed on the Gond's planet after two of it's crew were killed when their battle fleet came under attack by enemy fire, the two survivors going into stasis in their slurry form, manipulating the Gonds and draining their intelligence over thousands of years to initiate take-off. The Krotons were defeated when the Second Doctor destroyed their ship using sulphuric acid. (TV: The Krotons)
The Sixth Doctor later encountered Krotons on Onyakis who claimed the Dynatrope was an inferior model, and that their ship was more advanced. (AUDIO: Return of the Krotons)
The Master noted that a Dynatrope didn't have the capability to attack a TARDIS. (PROSE: The Quantum Archangel)