In the Silver Millennium he used to be known as Malachite/Kunzite (Kunzite in the manga). ( Malachite was the fourth "general" and his task was to pick up where Zoicite had failed, and retrieve the seven rainbow crystals. Anyway, when the Sailor Senshi found the entrance to the Dark Kingdom, Malachite met them there and tried his hardest to kill them all, as revenge since he blamed them for Zoicite's death. But, when all was lost, Sailor Moon took a stand and used the Silver Crystal on him. Malachite tried attacking Sailor Mon to repel the bright light, but she knocked his own attack back at him, and he was killed. In the manga he was a bodyguard for Prince Endymion.) After the battle with Queen Beryl Princess Serenity, who knew the old Kunzite was truly in love with Princess Venus, allowed the generals to live a normal life. She erased their memories of the Negaverse and send them to live in Canada. Later Mina might Ken outside her dorm room. During a battle with the Sun Knight, Ken turned into Kunzite. The Star Locket powered the generals into Planetary Knights.
