Hmm. I like a "Return of the Ether Lords" theme as an idea. Start with human followers (astral/death mages, recruitable everywhere, best mage SSD? capital only), default priests, weak light/medium infantry with independent strength archers (shortbows).
To use a mechanism already in place, give them a summoning site (akin to R'lyehs) in their capital which allows an astral mage to summon in reinforcements. The stronger the mage in astral, the stronger the Ether reinforcement.
A mage of astral skill S and death skill D will receive one pack at random from the categories allowed by his skills from the following list per turn.
Code:
ReqS ReqD
1 0 1d6+S Troopers
2 1 1d6+S Warriors
3 1 1 Champion[leader SSD?]
4 1 1d6+S Troopers + 1 Champion
5 1 1d6+S Warriors + 1 Champion
6 2 1 Lord[leader SSSDD?] - make lords produce 1 astral gem and 1 death gem/turn
7 2 1d6+S Troopers + 1 Lord
8 2 1d6+S Warriors + 1 Lord
9 3 1 Prince[leader SSSSDD??] - make princes produce 3 astral gems and 2 death gems/turn
Chance of insanity depending on astral strength. (Ether beings being nearly immune)
Then give them two special spells, "Summon Ether Troopers" (SSD, 10 Astral Gems for 5 Ether Troopers) and "Summon Ether Warrior" (SSSD, 3 Astral, 1 Ether Warrior"). Alternatively, give the leaders "Summon Allies" ability. (Champion->1xTrooper, Lord->1xWarrior, Prince->2xWarrior), though that would perhaps be too powerful given the substantial odds of getting an extra leader per turn for somebody who made an Astral 9 pretender.
Together with Ether Gate, that should allow the player to summon ever larger Ether Armies.... Either slowly through the gate back in the capital (a steady trickle of good to excellent forces) or through summoning at the cost of a lot of astral gems.
One completely sick idea would be to give them a base income of 10 astral gems/turn and the handicap of automatically changing all gems to astral gems (1 astral for each 2) corresponding to automatic use of alchemisation after site-income has been added to the pool each resolution phase. They do drain the world of other magic than themselves, right? If you want to use other types of gems, you'll just have to alchemise back and use them during the same turn (or store them on scouts...)
