[GavinWheeler]

We already have Elder things (called exactly that) as one of the Void Summons.

Shoggoths also have a clear analogue in the Lesser and Greater Othernesses, or the Formless Spawn

Deep Ones could be represented either by the Atlantians or by the hybrids that pop up in any coastal (on the land) forts you may build - that bit in the national description is not just there for colour!

This is not to say that there is no point in adding on your own personal interpretation of these. Personally I saw the Shoggoths as something the Elder Races made, rather than calling through a portal, so would have represented them as a High-level construction item, similair to Golems. But no two Dominions/Lovecraft fans would ever agree on the 'right' way to represent R'lyeh!

Mi-Go would be nice (for R'lyeh) in that they would be (if I recall correctly) cold-loving land-based troops that would nicely complement a R'lyeh taking a cold scale, as it often does since its sea-based troops are snug and warm under the waves. But does R'lyeh really need more strengths?