Located in the Mutters Spiral galaxy, Spiridon was closer to Skaro than to Earth. The planet was remote, distant from the vast majority of space lanes and located in an uncontested region of space. The planet had a low mineral wealth, perhaps due to its high concentration of molten ice "lava". The planet was located within striking range of the Thal homeworld (New Dhavius) during the twenty-sixth century. This fact alone placed it outside of Earth's sphere of influence as the Thals in this period still considered Earth to be a name from their mythology. Despite, or perhaps because of, this general lack of interest, the planet became home to a Dalek research facility during this time period.
In addition to a large amount of non-lethal vegetation, Spiridon was home to a large number of hostile life-forms. Some of the plant life of the planet was sentient to a degree and capable of following potential prey with eye-like growths. These plants also emitted a powerful toxin which was lethal to all other life on the planet. The native sentient life, the Spiridonians, developed an unusual defence mechanism – invisibility. These natives remained content with a relatively primitive level of technology.
The planet Spiridon was a world that, like Earth, consisted of a varied eco-system. The planet sported areas of jungle side by side with clearer flatland and both its lowlands and mountain regions were dotted with Ice Volcanoes. These natural features – thick jungles and liquids cold enough to kill a Dalek creature instantly through the casing of the Travel Machine made the planet an unlikely location for a Dalek research base and staging area.
Perhaps because of its apparent lack of suitability, a base was established by the Daleks on the planet. The base served two purposes. Primarily it was to become a staging area for a secret army of Dalek units which were to be upgraded with the results from the base's second purpose: invisibility research. This technology would vastly improve the Dalek war machine's effectiveness if it could be successfully developed. In addition to this special task force, an army of Dalek units had been stored in suspended animation in the planet’s ice caves. Despite their best efforts, the Dalek research unit could not create a stable form of invisibility – all their test subjects were driven insane or ran out of power after extremely brief operational periods.
A Thal taskforce, together with some of the natives and an alien identified as the Ka Faraq Gatri successfully neutralized the Dalek forces by burying them in ice lava. A deadly virus being developed in the laboratories was released into the Dalek bunker, which was sealed off and the surface base was destroyed. To all intents and purposes, the Daleks had been defeated and the planet Spiridon was ignored or forgotten by Dalek forces as they continued to wage war on all fronts. Long centuries of peace for the natives followed and the Thals a lso lost interest in the world.
The peace was shattered when Davros, fleeing the Emperor Dalek's forces, arrived on the world once more. With knowledge he had gained from the Doctor, the creator of the Daleks managed to revive the Dalek forces entombed within the ice and re-program them to become subservient to him. The planet became home to the first million of Davros' Imperial Dalek faction. It was also on Spiridon that the Abomination, the first Special Weapons Dalek defected to Davros' side. Following a brief battle which ravaged a portion of the planet's surface, the new Daleks left Spiridon, pursuing their enemies back to Skaro.
For centuries after Davros' forces left the planet for a more defensible location, the native Spiridonians maintain a peaceful existence without outside interference. In order to maintain the peace, the Spiridonians found a way to nullify their invisibility in an effort to deflect any interest in their world. In addition, they renamed their world Zaleria and themselves became known as Zalerians. The misdirection works for around a thousand years and although many Zalerians learned to forget their past, the ruling Elder councils never did and were ever wary of outsiders.
This wariness proved to be more than paranoia when the Daleks once more arrived on the planet. The invaders were in search of a lost Dalek army and also desired to resume their research into invisibility to aid their conquest of Mutter's Spiral. Ultimately they were defeated and the last of the buried Daleks were destroyed. The planet would once more be forgotten by the Daleks thanks to the rebellion which ate away at their hold of the galaxy. Though portions of the world had been devastated by the Daleks' bombardments, the planet and its inhabitants could once more begin a process of recuperation.
