Current questions and answers regarding the map editor.

Yes, technically speaking, that's correct. However, I don't think they can be summoned. For that to happen, they would need an ID from the list of IDs assigned to monsters, but they don't have one. On the other hand, the Warlock in the final mission of the sixth campaign somehow managed to place a wall. It was probably defined in the map objects rather than through a script, but in any case, it might help you. Take a look at how it works.