Based on Tahm Kench, Evelynn and this new post from Interlocutioner it seem's as though Demons in Runeterra are personification entities. Beings that embody the qualities of an intangible thing. In this case it seems to be human vices. So what other human vices would be fun to see as characters in the League of Legends universe? Personally I'd go for a Gambling Demon.
Nik Nikerson6 votesI was under the impression that Demons weren't really based on vices, but were spirits that had evolved to feed on negative energies. Fear isn't really a vice, but it seems to be what Nocturne thrives on.
DrawDiaGrams1 votesIs there a text you could point to for that? Also if true what do you think of an expectations Demon from Piltover?
mrmeddyman4 votesDemons copy emotions Aspects embody concepts Yordles adopt cultures
It all seems to be connected
DrawDiaGrams1 votesWhy didn't i see it before, it was right there in the Teemo skin. Yordles are.... Darkin!!!
Whyte Lyon3 votesIt will never become a champion (not that I think it should either) but without a doubt there would be a demon exploiting human bigotry/prejudice.
In light of very recent events here, fuck human vices and the misery we bring onto others.
DrawDiaGrams2 votesI donno I bet if they gave it the right treatment it would be a champion. Where would it come from Demacia? Piltover?
MankeyMadness2 votes[{quoted}](name=Whyte Lyon,realm=OCE,application-id=6kFXY1kR,discussion-id=1IJVkam7,comment-id=0000,timestamp=2019-03-17T20:15:48.222+0000)
It will never become a champion (not that I think it should either) but without a doubt there would be a demon exploiting human bigotry/prejudice.
In light of very recent events here, fuck human vices and the misery we bring onto others.
So basically the entire nation state of Demacia
No thanks, "current events" make for awful story telling. The less Riot references real world trends in their lore the less Galios we get, and thus the more readable the lore gets.
Whyte Lyon3 votesLike it or not, the fundamental world building of fiction is always drawn upon 'real world trends' (although they're not always modern trends) even if the fiction isnt trying to be social commentary. So I'm not sure what point you're trying to make. Nevermind that I wasnt even remotely suggesting this particular topic should reflect real world occurrences anyway.
On your second point. I would personally argue Ionia is way more attractive to a demon and susceptible to its influence, if it was in inclined to invoke prejudice and radicalization. Plenty of reason for even a demon like Nocturne to exploit Zed's nightmares.
GreenLore2 votesActually 
is based around all sorts of vices, he just chooses to describe them all as gluttony.
In fact Tahm is already heavily associated with gambling, as there are 2 stories where he interacts with gamblers(in the first one, he helps the gambler to escape his debt only to mess up his life once the gambler found happiness. In the other story he gives a poor gambler a coin to encourage him to gamble even more).