Draven can cash in off of Illoai's test of spirit
Together bot they can repeatedly cash in from passive and completely snowball out of control. I'm sure this isn't intentional.
2 Comments
1st Illaoi E can proc dark harvest and give you stack itself ( meaning the spirit is a seperate champion that is capable giving a dark harvest stack).
2nd Draven need to last hit the spirit. You can prevent that by attacking from afar illaoi so it reduces the duration. You can just go out range and become a vessel for a little -dodge the tentacles- and come back and fight them.
3rd You can poke draven when is going to grab his axe so next time he will have to choose between grabbing his axe or avoid poke and damage.No axe no stack to get.
4th This interaction exists at least 1 year now but only recently a high elo player made it famous and they start to abuse it.
5th Although this can lead to some crazy snowballs , both of them lack escape and CC ( Illaoi conditional slow is unreliable and Draven E duration is very small). So bring cc like knock ups or knock backs from support or jungler and you can shut them down early.
6th This work only if you let Illaoi land her E on you in the first place. So If you see her coming close then back out or get behind minions. In case she lands it attack illaoi and the vessel will disappear quickly or quickly run the other way to leave so they wont have the time to kill it.
7th Funnelling is still a thing and the funnel strategy is more snowbally than this one. Also a fed riven or vayne or at least with couple items - who are straight up S tier picks for months- can break apart draven and deny cc illaoi so she cant get any value from her ult.
8th It helps to have exhaust , it helps you survive once every 200 secs and have your team build 
,
,
,
,
that have grevious wounds that reduces the healing the illaoi get from her tentacles and you can burst her ( use 
too it can deny her healing and win a major fight cause of it).
9th Learn to zig zag to avoid their skillshots and hide behind minions. Also you can learn to freeze the lane close to you tower so they cant get a gank or kill you unless they want to towerdive you.
10th Learn to play against them. They are stong but i find someone like riven,sylas,vayne,zed bigger issue in the low elo cause they can snowball on their own and be a headache. But Draven-Illaoi is more manageable in my opinion.
the way riot have things coded its pretty much anything that looks liek a champ or is a revive like sion as a champ its gonna proc those effects tbh