Sicarious
Servant of Sithis
I didnt see this previously mentioned...May contain a mild spoiler.
"Secret of Arcana" is gained in the Dragonborn quest and it allows you to cast magic for 30 seconds at no cost. However if you continuously use a spell uninterrupted the time does not run out. Therefore with a spell like "telekinesis" you can end up leveling pretty fast, especially considering that the level cap is removed by allowing you to make skills "legendary" multiple times.
"Secret of Arcana" is gained in the Dragonborn quest and it allows you to cast magic for 30 seconds at no cost. However if you continuously use a spell uninterrupted the time does not run out. Therefore with a spell like "telekinesis" you can end up leveling pretty fast, especially considering that the level cap is removed by allowing you to make skills "legendary" multiple times.