[Taqwus]

Curiously, the dom2 binary has had inside it text description for a 'Portal' spell ("The caster opens an arcane portal between his current position and another province. Any number of troops may enter the portal in either direction. The portal will Last for one season unless the caster uses extra gems to enhance the duration. Each extra gem spent increases the duration by one season. The forming portal will be noticed by the people of the targeted land and enemy spies and armies might sneak through the portal.") for quite some time I think. I've never figured out a way to access it, however; it's either disabled or very, very secret.

There are other spells like "Arm the Weak", "Army of Ensorcelled Iron", "Wyrm Lord", "Teeth of Hydra", "Crystal Dome", "Beast Master", "Guidance of Gaia" which also have description text but I've never managed to see in-game. But then, I've not even played all the nation/themes...