Oberon

King Oberon was the Amadan na Briona of the Sidhe, or Fair Folk. As the king, and the spouse of Queen Titania, he traditionally represented chaos much as she represented order; he held himself to have a "duty" to do whatever he pleased and break all the rules, and Titania was not permitted to openly interfere or rein him in, lest she betray the nature of her own office.

During World War II, he helped both sides develop tanks which could phase into higher dimensions. Oberon travelled back in time and had degaussing equipment installed on the USS Eldridge, allowing him to be aboard the ship. The Eighth Doctor discovered this when he landed there with Fitz Kreiner and Sam Jones. The Doctor realised that Oberon was now pushing his limits, to see how much chaos he could get away with causing. However, Sam was really Oberon in disguise. He tried to kill the Doctor, who was forced to deactivate the degaussing equipment and trap Oberon on the misphased ship. When the ship later appeared in the rift between Earth and the Sidhe realm, the ship was destroyed and Oberon killed.

However, the Doctor was confident that Titania would find a "new" Amadan before long. It had earlier been made clear to Sam by Galastel that although there was only ever one Queen Titania, she could have diffetent "aspects", and one could be removed from office and replaced with another if she overstepped her bounds. (PROSE: Autumn Mist)