I am interested in this question: will the hero fight together with the army, or only the army without the hero? :)
Both the hero and the army will be present. How to do it is described here:
/topic/157/
You can download the arena file and try out your hero!
But everything is so easy and simple for Tournament Edition!!! :)
And if you haven't installed it, then you will have to do everything manually in the map editor. :(
Well, an example of an arena can be seen based on the results of the 2nd tournament – here:
/topic/113/