Hey guys my party is at the midpoint and wanting to return prince derendil home. I need some help figuring out what to do.

Little info in my campaign he is a Elf who was cursed and not just a mad quagoth. The cleric dispelled the curse and changed him back into elf form.

What I'm thinking of doing is having him have fallen in love with a drow princess when he was young. Then something happens, maybe they both get pulled away due to duty to the kingdom or something kinda almost Romeo and Juliette. I was thinking of it being the matriarch the party should meet in menzoberanzan (just can't remember her name currently) later for a potential big reveal.

Could use some ideas on how to make this work.

Originally I was going to make it a commoner who turned to a hag for help and then through a serious of bad decisions he gets turned into a quagoth but evening i wrote just didn't feel like it fit right.

Also could use an idea of how to run encounters and such for this middle section. Would a dragon be too much for 5 lvl 7 pcs, plus Asha, prince derendil and a maimed jorlan.