Evil Black Crystal

Not to be confused with the Black Crystal.

The Evil Black Crystal was a large black crystal from Sailor Moon R which grew stronger with more negative energy. It was a crystal from the planet Nemesis that Death Phantom used to try and destroy the Earth. The Black Moon Clan intends to let it grow enough to open the Black Gate and allow the world to be destroyed. The members of the Black Moon Clan, with the exception of Saphir, wore earrings made of this crystal.

In the anime, after the great battle in Episode 88, Usagi and Chibiusa used the power of their two Silver Crystals to destroy the Evil Black Crystal once and for all via Moon Crystal Power.

In the DiC English dub, this crystalline substance was called the "Dark Crystal," in the Tokyo-pop manga translations it was called the "Black Poison Crystal",  and in the Kodansha manga it was "Malefic Black Crystal". The Kanzenban release calls it "Beguiling Black Crystal". The name "Evil Black Crystal" comes from the ADV DVD releases.

Original Anime
In the second season, the Evil Black Crystal was in the very heart of planet Nemesis powered by a reactor that greatly strengthened its evil. Wiseman had a large orbicular fragment of it which he used against Sailor Moon (as Neo Queen Serenity) and Chibiusa's Silver Crystals. The Crystal also acted as a key to open the Dark Gate. Black Lady attempted to fully harness and channel its vast amounts of dark energy into herself to obliterate the Earth.

Second Anime
The Evil Black Crystal plays a similar role it had in the original anime. Wiseman said that the crystal rivaled even the supremely powerful abilities of the Silver Crystal itself and it possessed the power to dominate everything.

Abilities
As a crystallized stone of pure evil, it has complete power over the element of darkness and is capable of projecting supremely strong and destructive bursts of evil energy, leaving destruction and decay in its wake. It also has the ability render anything or anyone directly linked with the Silver Crystal itself utterly defenseless and powerless. Cristal Oscuro