Nova

Stella was a Witch from a world long long before earth, She became a Magical Being, due this and her already powerful magic Stella accidentally made a black hole.

The Kingdom
Stella made The Kingdom to try an at least bring back her people since she couldn't bring back her loved ones. She made it so the world would have Magical Girls, Boys & Witches but found due this the people would kill the bigger animal's she'd make which only made it harder to keep control of her powers along with the ever growing black hole.

Sooner then she'd like the black hole had grown to the point where destroyed the world Stella had made, this made poor Stella even sadder then she already was.

Earth
Stella came up with the idea of not letting there be magic on the next planet she made, that meant when she made earth she made it so there couldn't be any natural Magical Girls since without them there wouldn't be any Magical Boys or Witches, the only problem was a spell The Rainbow Princess has casted that made it so there'd always be at least 10 Magical Girls