Queen Metallia (SMCU)

Queen Metallia is the supreme ruler of the Dark Kingdom, having been the one who gave Queen Beryl her power.

In the Cinematic Universe, she is depicted as a malignant, amorphous energy being, with her original body being destroyed when she fused with Beryl.

First encounter with Beryl
Beryl first encountered Queen Metallia upon the request of Queen Nehellenia, the ruler of the Dead Moon who also sought to overthrow the Moon Kingdom.

The rise of Queen Beryl
About 1000 years ago, Metallia called a meeting for her followers in the Dark Side Castle. There, she gave a rousing speech, in which she shared her views on the Moon Kingdom, as well as her vision of the future, which is of another great and terrible war that will soon mean the end of the Moon Kingdom with a victory for the Dark Kingdom, with images of the destruction of the Moon Palace and Metallia sitting on the throne punctuating her rhetoric.

Metallia, openly noticing the battalion of Senshi and Moon Kingdom forces that had infiltrated the rally, told her followers to stay calm as she created a dark energy circle to surround her and test the loyalty of her visitors and followers. She also described how the Moon Kingdom have fought her so mercilessly, executing her followers simply for believing.

When Endymion set his men on Metallia, she conjured a circle of dark energy around herself, and added an enchantment designed to test the loyalty of her followers: those who entered with complete fidelity and believed in her cause would survive; those who did not, would be engulfed and perish. The Knights of Endymion (Jadeite, Nephrite, Zoisite and Kunzite) and Beryl joined Metallia into the circle, with Beryl becoming the new Queen of the Dark Kingdom after Metallia uses an enchantment to fuse her soul with Beryl's body. Beryl then manipulated the dark energy to work as a weapon as well, sending balls and bursts of black fire towards her enemies, thereby killing them.

Sometime later, at the tallest spire of the Dark Side Castle, Metallia spoke with Queen Beryl from inside her body about adopting her new powers.