How do you upgrade troops?

[Nike-it]

Originally Posted by Snaggly Pete

I have a bunch of priests and I just noticed that there is a button on the troop info screen that says upgrade to inquisitors. But that button doesn't seem to be active. What must I do to upgrade my priests? Are there certain conditions that must be met first? Thanks

There is a skill for all classes which gives you the ability to upgrade priests to inquisitors. It the last skill in the mind tree. And it is available for all classes.