Dont forget the Broken Empire (base) theme. Actually my favorite. SG and AE have both a terrible Achille's heel in MP games : all other players will hate you. And your economy is so weak that you simply cannot pay good indep mages or troops (pillage is a short term solution).

Ermor Broken Empire is an excellent nation that combines very good troops with some astral and death magic.

Weaknesses:
- expensive mages (but 1/2 upkeep),
- all mages and priests, apart from the cultist, are vulnerable to Magic Duels.

Strengths:
- excellent infantry,
- Body Ethereal, the best starting spell of the game IMHO, and death gems to raise hordes of Behemoths (Enchantment 4) or Wights (Conj 3) which are very good with etherealness,
- Leave a few thaumaturgs where your armies just fought to get free armoured soulless (against strong indep, I often raise 30 undead after one battle).
- The Vestals lack punch and are slow to gather in numbers, but they're free and with battlefield-wide power of the sepulchre (+4 ATT and AP, better than fire-8 blessing!) they're quite good units. And since they're from site, you can keep getting them even under seige.
- Nether Darts.

AND you can still be friends with your neighbours and have a flourishing economy.

Cheers