I wasn't necessarily going to hit everyone with the wall of text that I created for Diana's backstory, but since it's already written...
TL;DR - Olympic medalist -> sense of emptiness -> MMA fighter -> emotional struggles -> found a better path
Diana's story
Diana was excited to return to the real world. She got to rejoin her larger friend circle and return to competitive gymnastics. Between her already incredible talent, and the skills she developed in the Realm, she succeeded at becoming a member of the U.S. gymnastics team, eventually winning multiple gold medals at the 1988 summer olympics in Seoul. It was the highlight of her life.
Which was a curse as much as a blessing. At 19, she had achieved the greatest success that a gymnast could expect to achieve in their life. Already somewhat "old" for a female olympic gymnast, Diana looked out at the rest of her life and wondered… what now? Was it all downhill now?
Where once she had little desire to return to the Realm, now she began to yearn for return trips. In the Realm, she was still a great warrior. Her skills could continue to grow. And she felt important.
In her early twenties, Diana became more focused on being a fighter. She trained relentlessly, and occasionally made solo trips to the Realm just to fight. She would always help those in need - the Realm never has a shortage of people in need - but she helped those people as much for the thrill of fight as for seeking to do good. In the real world, Diana began struggling to maintain her life. She couldn’t hold down a regular job, and she let her friendships wither.
As fighting became the singular focus of her life, Diana turned to combat sport as her real world career. Diana became a mixed martial arts prize fighter. As a former olympian, Diana attracted a lot of attention, becoming a popular favorite. As a former adventurer of the Realm, she was also quite good, never losing a fight. Diana was seemingly on top of the world again, but inside she felt hollow.
Diana had no close relationships, and her life was consumed by training and fighting. She kept in touch with the old "dungeons and dragons" gang and joined them when Presto called them back to the Realm. But the once optimistic, friendly acrobat was gone, replaced by a somewhat grim combatant always itching for a fight. It put distance between her and her old friends. Diana recognized this, but couldn’t find a way back to who she used to be.
As Diana approached 30, the MMA fandom began to lose interest in her. Although her age wasn’t slowing her down, she was still viewed as an "old timer". New bright stars were rising, and the promoters just weren’t interested in having her potentially defeat these up-and-coming money makers. Despair began to creep around the edges of Diana’s thoughts.
Not long after Diana’s 30th birthday, Diana witnessed a massive shooting star. Mere moments after that, Presto summoned her to the Realm - alone. The event Diana had witnessed had occurred simultaneously in the real world and the Realm, and it was no ordinary meteorite. It was the return of - Diana’s potential soulmate that she met during the party’s initial time in the realm.
Kosar had become a being of spirit and energy, living a life mostly in the celestial realm where he helped maintain balance in the universe. But he had sensed Diana’s sadness. He had returned specifically to help her. Kosar helped Diana tap into her spiritual side, guiding her onto a new path. With Kosar’s help, Diana began following a path towards enlightenment. She began developing her body, mind, and spirit together. She finally began to find her center.
Over the past few years, Diana has changed her life. In the real world, she is now an instructor of martial arts - both the physical and spiritual aspects. She works specifically with underprivileged youth, helping them navigate the obstacles society puts in front of them. She also regularly returns to the Realm - not to fight, but to commune with the mystical energies there. She doesn’t see Kosar much anymore, as he is forever burdened with his celestial duties, but she is able to communicate with him. Although not romantically involved, Diana and Kosar are platonic soulmates, sharing a bond few can understand.
Looking forward, Diana now hopes to find an emotional partner in the real world with which to share her life. She has conquered her fears of growing old and weak, now seeing that it is merely part of the grand cycle. Someday soon, she hopes to find someone to walk that path with her.
And, of course, if the Realm needs her to fight for it again, she is ready. Not for the thrill, but because it needs to be done.