Coin of Necromancy

This coin was an artifact of the Old Religion and an extremely powerful tool of dark magic. It was given to Morgana by her sister Morgause, before the High Priestess' death, but probably the sorceress just told Morgana what it was for, and not how to use it.

Morgana went to the Dochraid’s lair to seek advice on the use the magical coin. The Dochraid was one of the last creatures who remembered the time of the Old Religion and therefore knew its secrets. Morgana gave her the coin to inspect, telling her it was "the price of a soul", and the Dochraid was so enthralled by its power that desired to keep it, though Morgana swiftly refused. The Dochraid informed her that she would have to travel to the the Pool of Nemhain, the last of the five Gateways that separated the world of the living from that of the dead. Morgana had to cast the coin into its waters and focus her powers on it to raise a Shade from the dead. Morgana did so, and the coin was lost in the depths of the Pool of Nemhain (Lancelot Du Lac).

Trivia
This magical coin had almost the same form and drawing of the pentacle Merlin used to reveal the Shade's true nature. This is probably because the two sorcerers (Merlin and Morgana) had practiced the same form of magic, related to necromancy and Shades.