Dominions 3 lore and nation backgrounds !

[Sombre]

It might be that the devs saw the magic draining from the world, not necessarily from the mages. So less sites, less mythical races, more emphasis on blood and death (because this magic is more readily available from humans).

[LDiCesare]

A Marverni->Marignon transition still loses blood in the process of EA/MA (most notably the blood sacrificing ability).
Man doesn't really come from Tir na n'Og, since Tir na n'Og turns into Eriu (these being Irish whereas Man is more Welsh/Breton and Marverni Gallic).
I also forgot to add Ulm to the list of nations gaining Blood in the LA.