Well, I think I read something related to this in another thread, but I'm unable to find it.

I was thinking in the possibility of defining an "invisible building" (let's say "advanced_technology"), impossible to construct, without card, that doesn't appear in battle map, but that appears through scripting. This would be the requirement for some advanced buildings for barbarian factions, acquired by spying or alliance (I cannot figure out how to make it accessible by shopping).

Could anybody give me a clue about this question?
Or any other method to obtain the same effect.

Thanks in advance.