Globgor

The Meumans have been at war with the monsters since their beginnings. When the Meumans arrived, they settled in monster lands, but they were able to hold their own because over the years the Meumans were ruled by a queen from the Butterfly family who possessed a magic wand with which they could cast spells.
Throughout the time between the war between monsters and humans, the wand passed from queen to queen, never leaving the Butterfly family, until it reached Queen Solaria, the monster carver, a relentless warrior with a sword that condemned every monster to a painful annihilation, leaving a mark that expanded with agonizing pain until it destroyed the monster.
Globgor, the current prince of monsters, had secretly begun a friendship with Eclipsa, daughter of Solaria, and despite the risk, that friendship turned into a romance, becoming a couple despite the dangers
That night, as usual, Globgor slipped into Butterfly Castle, knowing that Eclipsa gazed at the rose bushes from her room at night while studying magic. She went looking for him, as her mother was on guard duty. When she was almost at Eclipsa's room, she heard footsteps approaching. Globgor quickly shrank as much as he could, fitting into Eclipsa's hands, who hid him behind her back, for it was Solaria who was approaching.
Globgor merely pressed himself against Eclipsa's back, holding his breath as he knew that Solaria herself stood before Eclipsa.

There was a time when the monsters lived in peace until one day the Mewmans appeared, taking over and expelling them from their lands, managing to stand up to them thanks to the magic possessed by their queen, who did magic with her wand.
Years, even decades, passed through generations of queens who inherited the wand along with the throne, and following the same course as their predecessors, they continued the war between monsters and Mewmans as the Mewmans took over more territory, mostly having huge cornfields.

One day, Solaria was crowned the new queen of Mewni, and her wand was a sword. Its blade was like a lightning bolt of a brilliant reddish color that, when it struck a monster, didn't cut, but left a pain as if it had. At the same time, it left a mark that condemned the monster or whatever it struck to a slow and painful death, as the mark spread, increasing the pain it inflicted. Queen Solaria was known as the Monster Slayer for being a fierce and relentless warrior, but there was a time when she carried a baby girl strapped to her chest every time she went into battle. This was her daughter, Eclipsa, who was born with spade marks on her cheeks, a characteristic of the Butterfly family.
Solaria used her magic to create formidable spells and thus created the Solarians, a formidable army with swords like hers, but by making them so powerful they are unstable.

Despite the differences and conflict between Mewmans and monsters, it could not prevent the princes of both sides from meeting, growing up together, and beginning a pure love affair between them, despite the danger their relationship posed.