Something about Dom3 I found interesting. The spell Streams of Hades summons a Kokythiad; but such a thing does not exist in Greek mythology. It is a perfectly reasonable type of naiad that could have existed, but apparently it didn't. It's very cool to blend mythology and fantasy in such a seamless way that you almost feel like the Greeks were the ones who messed up.
The idea could be futher expanded. Here's a little excerpt from wikipedia:
"These rivers had names and symbolic meanings: the five rivers of Hades are Acheron (the river of sorrow), Cocytus (lamentation), Phlegethon (fire), Lethe (forgetfulness) and Styx (hate)"
Cocytus (Kokytos -> Kokythiad) and Styx are the popular rivers, but there's room for additional content to be created around the other rivers.
Ague of Acheron - Ritual that spreads disease and sorrow through a province by poisonous water bubbling up from Hades. (Same alliteration as Claws of Cocytus, just a different effect. Could be Agony of Acheron if you don't like the word Ague.)
Summon Phlegethiad - W/D path to summon a F/D or F/W mage
Alright, no more brainstorming. I'm keeping the rest of these ideas to make my own game.