Fairy King Oberon

Fairy King Oberon aka Sugou Nobuyuki (voiced by Todd Haberkorn) is a fairy king of Alfheim, and the main villain of Sword Art Online in the anime and the light novel.

Pre Adventure Series
Sugou once held three hundred people and Asuna Yuuki captive and tried to marry her but was defeated by Kirito, and was sent to prison.

Adventure Series
Sugou was once a prince in Alfheim, and ruled under his father. When his father died from an illness, Sugou became the ruler and was dubbed Fairy King Oberon Alberich. One day he was informed by his messenger, that he has to marry a woman. One day, he was presented to Asuna Yuuki. Oberon was quite smitten with her but she refused to marry him. Outraged, he called forth his guardians to try and force her to marry him. His heart sadly fell to darkness and caused him to unleash the Heartless. One man took Asuna to safety by Heathcliff, and he was never seen again.