Alzarius

Alzarius was a planet located in the alternate-dimensional continuum known as E-Space. On this misty world, a spacecraft known as the Starliner crash-landed, killing all the passengers- natives of the planet Terradon. At a time of year known as Mistfall, that occurs every 50 years, the native life-forms undergo a rapid evolutionary process. They hatch as spider-like creatures from melon-like fruits, quickly evolve into amphibious Marshmen, then into human-like beings. These humanoids came to believe they were descended from Terradonian survivors, and made attempts to repair the Starliner ever since. Each Mistfall, the humanoid population was killed by the Marshmen, who evolved into a new set of humanoids to replace them. This cycle was broken by the Fourth Doctor and Romana, who helped the Alzarians finally repair and take off in the Starliner. The Alzarian boy Adric stowed away on the TARDIS when the Doctor and Romana left.