Dariens has many forms,from Tuxedo Mask, to Prince Endymion to the Moonlight Knight. In the original Sailor Moon, Darien lost his memory in a car accident, so he doesn't know his true identity. For the first half of Sailor Moon, he was running around as Tuxedo Mask and didn't even know it. He regains his memory but is then killed and then brainwashed by Queen Beryl of the Negaverse. In the first half of Sailor Moon R, Darien had yet to regain his memory, but on of his split personalities, Moonlight Knight, is created because he knows he must protect Sailor Moon. Darien is also Prince Endymion, Ruler of Earth, who fell in love with the Moon Princess 1000 years ago(Serena). Queen Beryl also loved Endymion, but she didn't want to compete with Serenity for him. She destroys Serenity, but Endymion was killed as well while trying to protect Serenity.
