Heres how to get Champion Skins. I answeredthis before, and have the answer. Basically do whatever the unlock challenge required, like play heliophage, then quit once it starts as it updates the challenge unlock for the game. As I stated on this thread:
Where can i find the requirements?
Or in the tab next to shop there is a challenges catagory/achievements, theres the character unlock page. Can see progress
Thank you, that helps. I have 100% in that tab.