Okay… I have a couple of ideas for the Meropos plot from my alternate universe (basically, a redesign and rewrite).
Let's start with the OCs.
Amber's personal servant is a girl about 2-3 years older than Amber. She is a good friend to young Lightvale and possibly possesses the soul of patience.
Sarah Fallenfair is the first child in the Fallenfair family (Cody and Maggie were born after her). She possesses the soul of patience and kindness. She discovered a spell that allows one to combine two magical traits into one, but died as a result of her own experiment.
Children of Ramset and Ramsha. In my AU, Ramset and Ramsha are the reagents of young Asgore. Ramset Savetrin was the brother of Asgore's father, who was the husband of Queen Dreemurr.
Castellar Dreemurr is the younger brother of Asgore Dreemurr and the prince of monsters. He hates humans because of the war and the plight of monsters. He dreams of revenge against humans. He loves his older brother very much, which is why he also participated in the murder of the children (who fell into Mount Abbot).
Richard and Augustus are acquaintances (maybe even friends) of the Chara who fell into Mount Abbot. Richard is the soul of bravery, Augustus is the soul of kindness.
Jessica Grey's brother was a child with the soul of patience who fell into Mount Abbot. Frankly, the Grey family was abusive and instilled in Jessica and her brother a hatred of monsters.
Jesse and Roy are cousins (Zia had a brother who is Jesse's father).
Zia was a traitless being, but Ozrich, despite this, loved her with all his heart. It was because of his love for Zia that Ozrich began a policy of helping those without magic. (Ozrich was the king of Justeco, while Zia is part of a noble family.)
No one knows that Jesse is the leader of the Grey Phantoms. Society sees him only as a nobleman with ties to the royal family.
Perhaps Clover is Miasma. (Thanks to Onessa.)
Lapis Lightvale disapproved of his daughter's marriage to Jasper. (Jasper was lower in status than Sapphire.)
When Amber was born, Lapis separated Jasper from Amber and raised her alone, wanting her to be a worthy heir to the Lightvale family business.
After the war, some monsters who escaped imprisonment in Mount Abbot migrated to other countries.