HOW TO GET CHESTS

Did you own the champ Did you have chests available have you already gotten a chest with that champ?

I don't know how the system works but, sometimes I get it on A+. But when I get a lot of S's I get a chest. and check the collection hover on the champ. it will say chest acquired or not. I get less chests from champs who I already got chests from. not sure if that is relevant or how that's the system works. but that's my experience with chests

Either you have already gotten a chest from that champion, ir you have ran out of chests you can get (im not sure when it resets and you can get more) (i think its about 4 or 5 a month, dont quote me on that though)