Tropes:

Virgin FMC
Fated Mates
Size Difference
Modifiable... Toy
Nonbinary Love Interest
FFM
Bisexual
Polyamory

Blurb:

A witch living a lie. An orc who’s never known love. A succubus seeking revenge.
Fated mates found in darkness.

Gretta, the mistake.
As the only daughter of the most powerful witch in the country, Gretta must uphold their reputation at all costs—despite having no magic. After 24 years of living a lie, she leaves everything behind, finding refuge with a mysterious orc named Novis. Only hours after realizing he's her fated mate, she's kidnapped. To Gretta's surprise, both Novis and a strange succubus come to her rescue, revealing that she has not one, but two fated mates.

Novis, the outcast.
Born with strange wings and scales, Novis spent his childhood being tormented by his clan. Exiled at ten, he sought refuge on The Glen’s outskirts, spending two decades establishing his life as a recluse. What he thought would be another evening of solitude changed when a mysterious woman appeared on his doorstep—the same one who’s plagued his dreams for years.

Ki, the reject.
Ever since Ki could remember, she hated being a succubus. Forced to work in a brothel at a young age, she did whatever she needed to escape—even if that meant killing every person there. After that day, Ki vowed to never touch another person again, especially a man. It’s been sixteen years since she escaped, and now the prettiest redhead she’s ever seen threatened to break that vow.

When a dangerous gang sets their sights on Gretta, her mates will do whatever it takes to protect her— even if that means sacrificing everything to save her.