[P3D]

I looked at Atlantis again, and experimented a bit.
Problem with EA Atlantis is their early expansion. Why?

The troops have mediocre protection and abysmal to mediocre (7-12) defense meaning they won't last long. Perhaps their most decent unit is the War Shamber, but that sacrifices the extra attack of the Shambler for some armor and shields - and won't get the Coral Glaive hinted in the description. Glaive, an extra point of attack/defence and a sharkskin cap would help them a lot.
Coral Guards/Pillars have just too high encumbrance to be useful with their single attack of 10. The two shamblers of the deep have abysmal defense scores besides their similar MR.
They have serious problems against Triton Guard and Amber clan independents unless they attack in great quantities (which Atlantis cannot afford with 250g non-sacred magi and 500gp BKs). And underwater capitals with the usual 3 neighbors means they will have strong independents next door.

The usual E9N4 giant bless is expensive, as none of the available pretenders start with Earth magic. And the BKs need magical armor to utilize it as all their starting equipment is a quarterstaff and a loincloth. They have a natural protection of 16 (with Earth) but they face either poison or tridents on the stronger independents. Some starting equipment armor+helmet, would help a lot - just slap on some Boots of the Behemoth and go. I'd also change the Dagon pretenders magic to W1E1 from W2, that'd fit better with the Basalt City thematic.

This means Atlantis needs a SC to start with, i.e. mediocre scales and restricted paths on the pretender - and they can afford neither.