The Dark Crystal is a gigantic dark crystal. It is the base of the Negamoon Family's operations, and the source of Wiseman's power.

The Dark Crystal existed in the future, and Prince Diamond wanted the Imperium Silver Crystal to combine it with the Dark Crystal to rule the world. While he was putting energy into its energy reactor (in the middle of the room, in an area like where the Negaforce was located in the Negaverse), Sapphire noticed that the Dark Crystal was volatile and fragile, and could explode if energy was put into it too quickly. He and Emerald attempted to warn Diamond of this, but he ignored them.

Wiseman gave Emerald a crown powered by the dark crystal. As Wiseman had planned, the crystal was too powerful for her and it transformed her into a dragon, which was killed by Sailor Moon. Afterward, what remained of the Negamoon Family - Diamond, Sapphire, Wiseman, and Wicked Lady (Rini turned evil by Wiseman) - moved to the past with the Dark Crystal, implanting it in the middle of Tokyo, where it continued to grow, its power increasing.

When Sapphire discovered Wiseman's true intentions, he took the control chip from the dark crystal to prevent Wiseman from detonating it. However, Wiseman killed Sapphire and took it back.

With the Dark Crystal's power increasing, at the top of the Dark Crystal resided the Dark Gate, which Wiseman intended to use Wicked Lady to open, with plans to send dark energy through her to destroy the world. Although Wicked Lady was turned back into Rini, the Dark Gate opened anyway, and it appeared that Wiseman was going to win. Powered by the Dark Crystal, he gained the advantage against Princess Serena (Sailor Moon transformed) in their beam struggle, saying "Now that the Dark Gate is open, the power of the Silver Crystal is nothing!"

Although it was stronger than one silver crystal, it was not strong enough to defeat two; Rini had the silver crystal of the future with her. Transforming into Princess Rini, she, along with Serena, were powered up by the other Sailor Scouts, and unleashed the power of both crystals in an energy explosion, which destroyed Wiseman and decimated the Dark Crystal. It did not explode; its energy reactor was destroyed with Wiseman, and the crystal dissolved instead.

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