Queen Nehelenia wanted to rule the Moon Kingdom, and knew her only chance to do so was to take the Golden Crystal from Helios, but he refused to give it to her due to her evil intentions, so she imprisoned him, but was imprisoned in a mirror by Queen Serenity.
The Moon Kingdom was later attacked by the Negaverse, led by Queen Beryl and the Negaforce. Most of it was destroyed, leaving it in ruins, but the Beryl and the Negaforce were defeated by Queen Serenity.
The Sailor Scouts were later taken there by the spirit of Queen Serenity during their battle with Malachite. Sailor Moon was later taken there in Sailor Moon S to receive the Moon Spiral Heart Scepter.