Arena

[manic crag]

I think it would be great if there was little training grounds, somehting similar to Mount and Blade. Reason why, because it can help with practicing your skills in fighting and build up the stats. Maybe also find great soldiers there to recruit. Not saying a whole stadium but a small ground to fight.

[north kiln]

I like your idea of an arena

but imo I think it should be instead a training ground that can be built, where you can fight your own companions and both of you can increase their attributes while doing training