If Rhaast in the new skin is from an alternate universe then..
What about the Rhaast in the odyssey universe ? If every skin universe theoreticaly has 1 of each champion wouldn't that mean that there is a Kayn in the dark star universe and a Rhaast in the odyssey one?
Also did riot say anything about the imperial skins ? They could be easily moved in the new universe with a little rework (the only inperial skins are for Lux and Xin Zhao)