Well, based on this rule, we could have easily used 2 built guild halls in the Stronghold villages.
there are 4 guild halls in the Castle
and they are relying on this -- they should have built 1 tower there, and not 2 at the Barbarians
then there wouldn't have been any questions, if the Barbarians also used the Teleportation scroll)))
but the funniest thing is, for level 5 scrolls, you could build them at the Barbarians, because there is no level 5 tower in the Castle :)
(с) Roger Zelazny