Thanks for the input, everyone. I went with Kael. I wasn't sure if it would be better to prioritize a champ for Arena to work on the Great Hall or Clan Boss. Cruetraxa certainly can cleanup in Arena, and will likely be my second 6*.
Kael for sure. The other one is really good but its more of an endgame champ so it would be much harder to build. Plus kael is more useful everywhere in the game