First, quickly go over the rough outline of the faction.

What is their name and its common shorthands?

Great House Redoran, House Redoran, Redoran

What is their niche in the world?

They are a Great House of Morrowind, one of the five ruling over swathes of the province. Their main niches as a Great House is provincial defense. They protect the western border and are the second biggest backers of the temple after the Indoril, making up the majority of Buyoant Arminger members. Redoran of less well-off marches also operate as mercenaries. They produce food for local consumption as well as arms and armor for sale across Morrowind. 

Their secondary niche is being the house of noble warriors, having values that resonate with the Imperial Legion and the Fighters Guild (martial prowress, a code of honor, service, and obedience).

Who is ruling them?

The current Archmaster is Bolvyn Venim, former head of the Ashes March.

Ruling with him are the council heads of the 5 marches: Morvayn (Skar Warden and ruler of the Ghosts’ March; currently limited to ruling Maar Gan), Sarethi (ruler of the Stones’ March), Llethi (ruler of the Waters’ March), Arobar (ruler of the Snows’ March), Ramoran (ruler of the Ashes March).

Due to necessities of waging war in an essentially undeveloped territory, the mainland councillors have been given temporary fiefs to develop and oversee, considerably reducing the Morvayn family's influence: Sarethi has taken stewardship over the Northern Ashlands, Arobar of the northern West Gash (including Khuul and Ald Velothi), Llethri of the territory south of Ald-Ruhn (nominally including Caldera), and Ramoran of the West Gash (including Gnisis). Finally, Bolvyn Venim has essentially taken over rulership over Ald-Ruhn itself for the duration of the crisis.

How is the faction organised beneath the rulership level?

The marches are administered by councils, made up of prominent Redoran families, Redoran Hetmen (rulers of settlements), and Redoran living in the countryside. Aside from them, yeoman farmers and clansteads dot the countryside but have a more flexible relationship to the march rulers, often operating under the protection of one of the above.

What is their outline?

Who founded it? When?

House Redoran was established shortly after the battle of Red Mountain. 

Warrior clans who had ridden war crabs in service to the First Council held a meeting near the carcass of the Skar, the greatest of them, to address the account of Alandro Sul, the problem of the now houseless Dagoth remnant, and the proclamation of the Tribunal.

After absorbing the former Dagoth members in mutual agreement, the clans split into two factions over Sul’s accusations. The greater part of them disregarded his accounts and formed House Redoran (with them being the most prominent crab riders and former operators of the Skar, nothing else would do) and the others becoming Ashlander clans.