I have had several ideas:
A locust/swarm character
The 3 fates who have on hit box but are 3 different models. They wouldn't be the all powerful beings of Greek myth but maybe just an interesting trio of witches, demons, or cult.
A cool and terrifying mummy that is trying to fully reform his body off the lives of others? Basically the mummy from The Mummy. Ammummu isn't that cool and badass imo.
A Warrior/Sorcerer with a snake. Maybe he can turn his snake into an arrow, shoot the arrow, then have it reform into a snake?
A Wolfpack caller. A guy who uses wolves? Maybe his wolves can move away from him and make him like an ADC and ranged?
A guy with 2 lynxes and a bow? Some connection to Swain as he can turn into a lynx-born with his ult? Maybe he and Swain did the same sort of ritual but Swain messed it up and tore his leg up?
You can look at some of my concepts in my profile. Gundari and Katyani are pretty cool.