[Fate]

I would point out that, while most the deep ocean is very cold, it is also mostly empty (for the same reason). Life in the deep sea is concentrated around the vents, so it would make sense a predator like Deep Dagon would want it.

On another note, I have thrown together my own take on Deep Dagon, incorporating some suggestions from HoneyBadger.

Changes include:
--No magic
--Pathcost increased to 60
--50 PR and Awe +0, but no fear
--Aquatic (not amphibious)
--Recuperation
--Autocasts Darkness (this is the only way to get darkness underwater)

The autocast Darkness synergizes rather well with the 50-100 DV that Atlantians have. I might reduce the base cost to 100 from 125, but otherwise I *think* he is balanced.

#modname "Deep Dagon"
#description "This mod adds the Deep Dagon pretender choice for early Atlantis."
#version 3
#icon "DeepDagon\deep_dagon_banner.tga"

--Spell slot used: ?

#newspell
#copyspell "Darkness"
#end

#selectspell "Darkness"
#researchlevel 12
#spec 8388608
#end

--Unit slot used: 2400

----------
Pretenders
----------

--Deep Dagon
#newmonster 2400
#name "Deep Dagon"
#spr1 "./DeepDagon/deep_dagon_1.tga"
#spr2 "./DeepDagon/deep_dagon_2.tga"
#descr "The Deep Dagon is an ancient Deep One grown to truly monstrous proportions. Like all Deep Ones, it has perfect darkvision and is highly resistant to environmental extremes. Deep Dagon has spent so long in the darkness that it now follows him wherever he goes. Though slow and plodding, the Deep Dagon is extremely powerful, has developed tough, armor like skin, and has gained skill in earth and water magic. The Deep Dagon has a great, cavernous maw, which it is not afraid to use in combat, often swallowing whole several smaller foes at a time."
#ap 6
#mapmove 1
#hp 200
#prot 16
#size 6
#str 32
#enc 4
#att 8
#def 8
#prec 8
#mr 18
#mor 30
#gcost 125
#rcost 0
#pathcost 60
#startdom 3
#weapon 461
#weapon 29
#restrictedgod 21
#aquatic
#coldres 50
#fireres 50
#poisonres 50
#blind
#stealthy 0
#awe 1
#startage 3000
#maxage 5000
#heal
#onebattlespell "Darkness"
#itemslots 15494
#nametype 117
#okleader
#end

Thanks again to WaywardG for the sprite, I hope you don't mind my posting an alternative interpretation.