Do players get most of their mythical champions from shards or rewards/fragments? 

I was struggling with one of the boss fights in Grim forest. I looked at the "best teams", to get an idea of what champs would help me out, and out of 30 players 29 of them use "Siegfrund The Nephilim", with most of them using only Siegfrund 😩.  (Stage E21 or 102) Something like that.

Hope I didn't miss a fusion 😢. I'd say that I'm probably just above a light spender, maybe 50+$ month (when I play) so my expectations of getting a mythical champ are really low. So that's mainly why the question. Are people just buying tons of primal shards and pulling mythicals? Or did I miss some fusions?