Trion (planet)

Trion was the home planet of the humanoid Trions.

History
Early in its history, Trion was attacked by the Tractators, an experience so traumatic to the Trions that it survived as an ancestral memory for millenia. (DW: Frontios)

By the 20th century (Earth reckoning), Trion was an advanced world with many colonies, some of whom were centuries old. (MA: Lords of the Storm) They had spacefaring and transmat capabilites, and were on the cusp of developing time travel. (TC: Turlough and the Earthlink Dilemma)

At around this time, Trion suffered a civil war. At least some of those on the losing side were exiled rather than killed; Vislor Turlough was among these. Even young children, such as Malkon Turlough, faced exile; it seems to have been applied to rebellious families rather than individual combattants. The exile was lifted by 1984, and exiles were permitted to return. (DW: Planet of Fire)

The Tenth Doctor and Emily Winter visited Trion to make sure that Turlough didn't write the diary that the Advocate was using to manipulate Matthew Finnegan. (IDW: Final Sacrifice)

Geography, Flora, and Fauna
One Trion continent, Slotisland, was reserved for Trion's other native species, the Slots. Slotisland was home to the Slotsruins, traces of the vanished civilization of the Laima, but the Slots kept the Slotsruins behind a force field to keep it secure from outsiders. (TC: Turlough and the Earthlink Dilemma)

The main Trion continent, home to the Trions, had an impossibly vast chasm called the Giant's Drop. It was a popular tourist attraction. (TC: Turlough and the Earthlink Dilemma)

Trion was also home to the Mobile Castle, a bizarre and ancient artifact poorly understood even by the Trions themselves. (TC: Turlough and the Earthlink Dilemma)

Vislor Turlough once described the trees on Trion as being three times the size of Earth trees, with plate-like thick mauve and purple leaves growing in spirals up blood-red trunks. (BFA: Loups-Garoux)

As Trion had vulcanologists (DW: Planet of Fire), it was almost certainly a volcanically active world.