Viridios was an entity that slept in the Earth for one million years, as a forest. A parasite, it fed off memories. It described itself as:
The spirit of the trees, the life force of nature. Viridios is the canopy of the forest, the creak of the branches in the wind, the roots plunging darkness to the Earth."The being inspired many Earth legends, being portrayed in myths as "the little green man", a symbol of rebirth.
Viridios awoke in 1960, the forest surrounding Stockbridge, and formed a stasis field around the town, creating a never-ending summer where no one could die. It used the Lord and Lady of the Manor, future versions of the Fifth Doctor and Nyssa, as puppets. Viridios fed on the happiest and saddest days of the Stockbridge locals, making them relive them all the time. The entity was defeated by Maxwell Edison's psychic power, and the "bubble" he'd created "popped". (AUDIO: The Eternal Summer)