Board Thread:Question and Answer/@comment-162.58.82.135-20150302155816/@comment-84.44.218.101-20150302180546

If one of them is in one of your units, be it attack or defense unit, and the other in your inventory, you will not be able to evolve them if you drag in the inventory card and then attempt to mark your unit card. remove her from your team and try to evolve then, or do it the other way around: drag in your unit-assigned card --> mark card in inventory