Crit based support character?

I just had a random idea for a support character that buffs allies this is a completely on the fly idea so I havent come up with any abilities or anything like that. I was just curious to see what people would think of that kind of character or if that kind of character exists in any MOBA not just league. Their abilities would allow them to manipulate crit chance, and crit damage for their allies and maybe even their opponents and maybe allies critting would allow them to cc or cc opponents they hit together. If I had to come up with a backstory I'd say this champion would be a gambler. A true gambler, do or die, not just well versed in card play like TF So please let me know your thoughts on this if it's been done if you think it'd be interesting. I'd love to discuss and see what the community has to say.