After picking whichever faction you want to learn more about, you can eventually become a Master of the guild and learn new skills for your character.
There are a good number of these factions, like the scholars at the snowy College of Winterhold, the secretive assassins of the Dark Brotherhood, or the cohort of rogues and bandits of the Thieves Guild. Total freedom in how you choose to play through the world's different factions You can set off to any of Skyrim's different towns and discover new storylines from interesting factions that flesh out the world and the lore, with great characters and their own absorbing narratives to get lost in.
