The tenth stage of the "Van Kanigem" tournament.

I found a description of machine development in the manual. There are two pretty cool levels. A ballista with three shots and the ability to intercept enemy machines and take control of them. Pages 133 and 134. That's the thing – I leveled up one of the heroes to level 23 just for fun!!! – but it still doesn't work, even though he has the required skills (this is about the rapid-fire ballista; I haven't checked about controlling machines). Is this disabled in the map itself, and if so, where can I find information about other nuances? The map is actually not that difficult; I read a bit, and it's already easier.