So I forgot to give some spawn ideas before, so I'll throw some out. Before that though, 3 things to consider: 1. I interpret the way you're going to do this as having "spawner" wandering creatures and gaurdian node protecting creatures, so in most cases I put the weakest first so they could wander and the more powerful second to guard; 2. I listed at least 2 usually tried to find 4, I don't know if you like the idea of it but what if wild mana nodes that haven't been conquered get more powerful spawns after a certain time/tech req./whatever? 3. The more choices I provide, the easier this should be on you. Anyway, here you go.
Death- Skeletons, revenants, haunts, horned dreads.
Entropy- Tar demons, pit beasts, hell hounds, beasts of Agares.
Dimensional- Gnoslings, thades, djinn.
Nature- Fawns, guardian vines, minotaurs, treants.
Life- Monks, angels, radiant guards, seraphs.
Shadow- Specters, ghostwalkers, mistforms.
Air- Lightening elementals, air elementals, manticore.
Body- Bone golem, flesh golem, bone horde(?).
Chaos- Freaks, abominations(?), chaos marauders.
Creation- Immortal (yeah.. this one was hard, so that's all I got)

Earth- Hill giants, earth elementals.
Enchantment- Wood golems, iron golems, clockwork golems.
Fire- Azear(I..think), fireballs/meteors (enraged?), fire elementals.
Ice- Frostlings, frostling archer/wolf riders, ice elementals.
Law- Host of Einherjar, demagogs, heralds, angels of death/seraphs(?).
Mind- Psions (that's all I really got..)
Sun- Lightbringers, Aurealis
Water- Drown, Ira, water elementals.
So a couple in there are insubstantial, but you could either repeat spawns (no one said they couldn't spawn the same things) or just make new units. The latter probably isn't worth the trouble though. Also, I really couldn't think of anything that great for force of spirit. I was thinking maybe spirit could have a mechanic that disallowed any combat in a 1 tile radius, but that got shot out of the air as soon as Deadliver mentioned something about settling on nodes, and then of course settling even near a spirit node would be unbalanced. Just thought it would be fitting if Sirona's nodes would grant a form of sanctuary really.
Anyway, there you are.

Probably cause you a headache with all of these posts.
