An oratorio is a large-scale piece of music for choir, orchestra and vocal soloists, which tells a story without staging or costumes. Most oratorios are based on stories from the Bible, a source that Handel's English audiences knew well.
Enthir is a Bosmer sorcerer and merchant found at the College of Winterhold, and has connections to the Thieves Guild in Skyrim.
An aspect of Skyrim's game play is the use of soul gems, and item enchantment. The game does explain how enchanting and soul gems work, but not in great depth. Contents (use the Control+F command to quickly find the info you need!) :: 1. General Soul Gem Info. 2. Black Soul Gems and Azura's Star.