To fix path finding issues, when opening a gate bettween 2 citys, do something like this:
Each city needs a pree built gate.
To connect citys you need to "explore the eather for a route" A space time relm thats differnt from our own, days weeks or months could pass for the people in the "eather" while only a turn passes for us.
Weak units could get killed to the nastys.
Once you create a route you still have drawbacks, including raids from the eather, possable backdoor into your city from other players (which would require geting a spy into your city) troops need to keep the route clear for city trade, and your "hero" would have to give some of his magic to keeping the gate open, OR you need to train lesser magic users in the city (and reduce the magic the city gives the hero)
Finally repeated trips through the "Eather" could age units due to the differnce in space time, which would show up as hurt units etc.