Thallonian Empire

The Thallonian Empire was an extremely xenophobic society located in Sector 221-G of the Beta Quadrant, located between Federation starbase Deep Space 5 and the Romulan Star Empire. ()

For centuries the empire was ruled over by a royal family who were based on the Thallonian homeworld, Thallon. By the mid-24th century numerous civilizations, including the Nelkarites, had been conquered and forced to become subjects of the empire. Naturally, the Thallonians were extremely protective of their territory, and any unauthorized trespassers that were caught inside their space were sentenced to death.

The Empire finally collapsed in 2373 following a coup d'etat, which had been engineered by the neighboring Danteri, and had left the majority of the royal family. Following the break down of law and order, the collapse of the Empire was swift. Hundreds of thousands of refugees poured out of Thallonian space into neighboring Federation territory. (' : '; )

In the late 2370s, the sole survivor of the Thallonian royal family, Si Cwan, drew many of the former subject worlds together to form the democratic New Thallonian Protectorate. (' : '; )

Alternate timelines
In an alternate timeline experienced by the crew of the USS Infinite in 2382, the Thallonian Empire never collapsed in 2373 as the royal family were able to obtain intelligence pertaining to the Danteri's plan to engineer a coup, and out of desperation made an alliance with the Dominion and the Cardassian Union. With the aid of the Jem'Hadar, the Thallonians were able to invade Danteri territory and put down any resistance within their own borders.

Despite the respite, the collapse of the Empire was inevitable and, following the Federation Alliance's defeat of the Dominion in late 2375, the collapse finally occurred as the people rose up and executed their leaders for selling them out to the Dominion.