Who would you pick to level up next?
I vote for Costume Colen.
I would do Kelile and costume. She is fast mana, so her special is at the same time ready as Scarlets. Together the ladies can kill any 4* in war or tournament.
My vote goes to Khagan. In combination with your Boldie and Wilbur he will shine in events and against double formations
In the minority here, but that bottom row would be the most ideal to level next. Sudri > Ei-Dunn > Hawkmoon > Bauchan > Vollermork. Quick and cheap and very fun heroes to play with.
I would do Kelile + Costume and then Khagan. They will help you in war and events
First Costume Colen and then khagan. After that the 3*s. Costume Hawkmoon, Surdri, Bauchan, in that order.