Primal Dalamud?

[Enkidoh]

EDIT
A side-thought, it's possible that the Lambs never really did communicate in an organized way with any specific entity, but just got targeted by whatever void denizen first stumbled across their invitation to Darkness while they were messing around with their stolen copies of the Necrologos.

I think this is perhaps the most likely theory - remember back in Tam-Tara NM, when Mindflayer!Galvanth is first summoned? His comments seemed that the Lambs really had no idea what they were even summoning (the voidsent wearing Galvanth's name sure didn't!):

King Galvanth the Dominator: "Who summons me from the Void to inhabit this crude vessel?!"
King Galvanth the Dominator: "You seem surprised. Did you not cross our gates in search of blood?!"
King Galvanth the Dominator: "Come hither, children of the Dawn! The undying master will drink deep tonight!!"

It just seems to me that the Lambs were basically dabblers in the dark arts, united by a vague "We believe Dalamud was a god who will ascend us to heaven blahblahblah', but really, they had absolutely no idea what the seven hells they were doing. Unfortunately for us, that doesn't make them any less dangerous, perhaps more so.