never forget where you came from...
There are several factions to choose from on Imperion, each with different goals and ideals. The majority of the character-base, most likely, are liable to be involved with, or a part of, the United Republic, however there are factions in the Outlands to choose from, too. While the United Republic refers to them all as 'the Outlanders,' most of them are not really affiliated with the rest, and may even be enemies.

The Andascan Federation is a union of fighters from the city-states of Andasca, essentially a defence force, and the first and only military that Andasca has ever had. While non-battlers are permitted to ally with and join the Andascan Federation, most are either Losrian, or Other. The Federation is, in some sense, also a unifying government body, that brings together the rulers of the remaining Andascan city-states into a single, overarching government, ensuring the city-states remain united, and operate as one.

The Dragons of Circinus have existed for far longer than there was a such thing as an Outlander, but none now live who remember a precise year earlier than 1819. It is believed, however, that they have existed at least a hundred years longer than the United Republic.
The Dragons are perhaps an enigmatic Outlander group. While they fight the United Republic's encroachment, and harbour many an anti-Republic sentiment, they are neither truly against the Republic, nor for it. The Dragons see no one as enemy, and no one as friend, and are as close to being a neutral party in the Outlanders versus Republic conflict as is possible.

The establishing group of the Dome, and the perpetrators of the separation between human and Other, as well as Dome and Outlands, the United Republic rule and oversee the Dome. The vast majority of the human race lives in the Dome, and thus is under the Republic's protection, but they are first and foremost a military, and their government style is heavily leaned toward military-state governing. The Republic does not ask. It tells, and its people either fall in line, or they face rather dire consequences.
Creating Your Own
As our factions are driving parts of the game, creating a custom faction, while absolutely possible, is a little more complex than simply giving it a name and logo, and calling it a day. Non-competitive factions can be created this way, however they cannot gain star-rankings, or be considered "big guns."

In order to create a competitive faction, and gain access to all the perks that are available for those, such as star-rankings, resources, income streams, and the ability to participate in territory battles and declare an alignment, a faction will need to complete a certain quest chain. This quest chain will be released at a later time.