I've been playing for awhile and have all the normal factions on my list, but I recently joined the 'Order of Virtuous Blood' and I thought that was awesome because it added another faction to the list of factions in my profile, does anyone else know of factions you can join besides the main one's.
Knights of the White Stallion. From memory yougo to Leawiin and speak to the count, who will set you on a quest. Follow the quest.
You can also join "The Knights of the Thron". You have to save The count of Cheydinhal's son from the Oblivion Gate out side the walls. if he lives, then he offers you to join the The Knights of the Thron.
in the main quest when you infiltrate the mythic dawn to steal the mysterium xarxes for the shortest time inbetween when you put on the robe and when you steal it, you join the mythic dawn for a small period of time. yum.