[Verjigorm]

I use the Wight Mages on excursions outside my own dominion frequently. For inside dominion attack and defense, I have Lichs which are much more expensive, but permanently immortal. Twiceborn is wasted if my Augur Elder dies in enemy territory, and I would prefer to take a 2F1S4D Wight Mage that only cost 10 (8 in the current game with my nexus) gems into enemy territory than a lich who can't die in my dominion that cost 30 (24) gems. Also... I found that Teleporting to your own province when it has a Dome of Flaming Death up is also a convenient way of transforming Twiceborned mages, but since you lose all of his gear in the process, it's more money than it's worth (Yes, I wasted a Starshine Skullcap).

The other recruit-everywhere mage, the Augur, is FS, and while useful for research and a bit of Evocation (in reverse communions especially), pales in comparison to the raw power you get with an Augur Elder which can be used in the same fashion.

I selectively transform my Augur Elders with Twiceborn when an Augur Elder comes up with 3D because the transformed Wight Mage with then have 4D which means he can go into battle with 5D or 6D depending on equipment which he doesn't really even need to be awesome.

I build fortifications opportunistically to defend multi-site provinces, recruit larger numbers of interesting indy units or for strategic positioning. I rarely base the choice of location on the cost or build time of the fort. "Swamp" or "Hill" terrain would be a far-off 4th ranking criteria after:

1. Special Site
2. Interesting Independent Unit
3. Strategic Position

With those three criteria in mind, I usually don't have the extra money to build forts purely on the basis of terrain type.