Fungal based champ?
A champ who's passive is the building of fungal organisms in allied/enemy units. The organisms build over time/aa kind of like cassiopeia, but per champ and maybe they'd be wiped on infected unit death. Abilities gain additional effect with amount of infection. Probably a void champ that feeds on other void creatures as a background. I'd think the gameplay would be about building infection in as many enemies as possible to as high a degree as possible then using abilities that go from root to stun, fear to charm/taunt, mana/hp drain to stat drain.
An ult idea would be disperse where the the champ explodes into a cloud of spores, becoming untargetable and greatly increasing infection to champs in the cloud, and finally after a delay or on click materializing at a target location within the spore cloud. This wouldn't deal damage to enemies but the aoe spore increase would be pretty strong for all his other abilities. So it basically turns into a really could counter engage champ. See an enemy amumu/malphite leading the other team into a fight with your badly positioned team? Disperse, see how many champs you can get in your cloud, materialize into a good position and start using your qwe for damage/damage mitigation.
I guess it's kind of like vlad/cass but maybe less damage for more utility? ALSO void support that isn't a vel koz who didn't get mid!