10,000-8000 years before Year Zero: The First Ones, a race of non-human Ancient Ones with tremendous magical and supernatural powers, first migrate to Etheria via magic space portals from the planet Eternia. The First Ones build the Crystal Castle and make one of their own, Light Hope, its guardian.
8000-5000 years before Year Zero: Predominantly human exiles from Eternia who worship the so-called Old Gods flee to Etheria because of the rise of the Goddess cult on Eternia.
5000 years before Year Zero: magic space portals between Eternia and Etheria (mostly) shut down.
5000 years before Year Zero to Year Zero: during this period, the First Ones and the more human inhabitants engage in a political, sometimes armed, struggle for control of the planet.
Year Zero to Year 345: the struggle between the First Ones and the humans of Etheria continue.
Year 345: Thanks to mediation by Light Hope, the humans of Etheria submit to the planetary rule of the First Ones.
Year 1451: the First Ones except for Light Hope disappear into the core of the world. Establishment of the traditional, monarchial government of Etheria with a male ancestor of Queen Angella as the first human planetary monarch of Etheria.
Year 2965: Evil Horde first invades Etheria. The Council of Kings goes into hiding, but they are betrayed by Shadow Weaver, apprentice to Norwyn the wizard. Hordak becomes the de facto planetary ruler.
Year 2981: Queen Angella assumes leadership of the traditional, legitimate government of Etheria after her father, the previous ruler, dies in combat with Horde forces.
Year 2984: Angella's husband and political advisor King Micah captured by the Evil Horde and held as a political prisoner for 15 years.
Year 2999: events in the series She-Ra: Princess of Power take place.