Sep 21, 2021, 06:0709/21/21
You can upgrade the champs in the tavern to increase their basestats. The stars get pink if you do so. Also the usage some artifact categories are bound to these stars: only champs with 5 pink stars can use Amulets and to use Banners 6 pink stars are required.
I highly recommend to read this thread. For your question especially the part about "Ascension".