The Element of Darkness was inspired by the Rainbow of Darkness from the animated television special Rescue at Midnight Castle. In addition, both items were created by a Generation 1 and 4 villain. Originally, the Element of Darkness was supposed to have once been a part of the Tree of Harmony, but the idea was scrapped.
HistoryThe Element of Darkness was created by Lord Tirek, using dark magic, some time before he and his brother Scorpan came to Equestria in order to use its power to assist him with his plans. As Tirek was imprisoned in Tartarus for his crimes, Scorpan hid the artifact someplace deep within the Everfree Forest in hopes that it would never be found by anyone, before returning to his homeland.
Some time later, the Element of Darkness was discovered by Atronnus and fused with him, causing Atronnus to transform into a new dark form.