Dominions 3: The Awakening/Nations/R'lyeh, Time of Aboleths

Before the Great City fell and destroyed their capital, the Aboleths ruled the seas. While the bulk of R'lyeh's armies are still shambler and Atlantean slaves, their elite units and commanders are Aboleths of various ages. The oldest Aboleths are extremely skilled in both water and astral magic.

Units

 * Unit: Gold x, Resources y
 * Description

Commanders

 * Unit: Gold x, Resources y
 * Description

Heroes

 * Auluuhd the Mind Lord: W4S4 aquatic, magic being, darkvision(100); hp:99 prot:2 mor:13 MR:20 str:15 att:10 def:14 prc:10 mv:2/5 ldr:10

National Summons

 * Unit: Gems z
 * Description

Globals, Globals, Globals
Turtle-up underwater and push research everywhere to leverage your powerful magic asap. Take a pretender that can easily cast high-level global spells: Make Claymen once you have a strong E income and move onto land using Communions with your N amphibious mages, dominate in tough fights using Foul Vapours (this tactic doesn't work vs undead nations nor constructs, but against an unprepared opponent it can be quite deadly).
 * Enchantment, Gift of Health, Stellar Focus, Earth Blood Deep Well, Haunted Forest, Arcane Nexus.
 * Alteration, Mother Oak, Sea of Ice (use a Mind Lord) and Wish.

Scale Design

 * Sloth 3, Cold 3, Magic 1. Admittedly very severe, but we are not going to dominate on land with our native armies, so all we need is enough to take over the seas, then turtle up till our research is improved and have a healthy gem income. This gives us points to take an awake pretender with the high magic picks we need. If you prefer to take the pretender dormant, you can afford some Order/Growth.

Pretender Design

 * Void Lurker, Awake: E6 S7 D2 N5 B2, Dom 7. Awake pretender for researching on turn 1. Bless grants +2 MR, +3 Reinvig, 5% regen. Astral allows it to teleport. With the right magic buffs, should make a pretty powerful defensive SC caster, and can even blood hunt a bit on land. Can cast most globals from the Enchantment school without requiring boosters. Only needs a Crystal Coin to be able to cast Wish or Arcane Nexus. Easy access to Dwarven Hammer, Blood Stones, Lamia Queens, etc.

Expansion
Take all underwater provinces and use your N randoms to search for free Kelp Fortresses. Between Voice of Tiamat and your D-random Aboleths, you should be able to find most magic sites underwater. Crank out slave mages for research, you need those E/N random picks for combat communions on land. Don't worry too much about getting onto land till you have the magic and summons to back you up, otherwise you are just going to waste resources and likely get pushed back into the sea by a land power. But even a single land province can offer a place to blood hunt for making Blood Stones and setting up a lab for diverse summons. You can get magic diversification through Lamia Queens/ Specters (both at Conj-6) and Hidden in Sand/ Snow (ench-6).

Research Order
Detour into other schools for low-hanging-fruit battle magic as needed.
 * Conjuration to level 4 for Voice of Tiamat.
 * Thaumaturgy 1 for Communion Master, Communion Slave.
 * Construction 2 for Dwarven Hammers, Crystal Shields.
 * Alteration 5 for combat buffs, Encase in Ice, Bone Melter and Mother Oak.
 * Construction 4 for Amulets of the Fish, Blood Stones, Crystal Coin, other boosters.
 * Enchantment 5 for Claymen, Foul Vapours, Gift of Health.
 * Enchantment 7 for Stellar Focus, Earth Blood Deep Well.
 * Enchantment 8 for Haunted Forest (if you are in a land war).
 * Enchantment 9 for Arcane Nexus, Gift of Natures Bounty (if you need it).
 * Alteration 9 for Wish.