[Quitti]

Well, certainly you can't give +1e just to all ulm mages. Nor Agartha.

Here. Have some rambling about the tome, nature and blood magic.
Currently from what I've gathered, the best way to get your bloodstone economy going on ulm would've been to take a forge lord with blood or something similar - now it would only change to force the forge lord take some nature instead of blood. For agartha I've always just hunted with indep scouts for the slaves, though I don't see why they couldn't have done something similar with blood access -pretender. Do also keep in mind that if you are taking nature on your pretender(+n4), your sacred units will get regen, boosting your sacreds usability a lot (priest smiths for ulm, ancient ones/lords/oracles etc for agartha). It would be an indirect boost. Combined with the fact that you'll be having earth on your pretender also - that's reinvig (and perhaps prot if you go all the way to 9 or 10). Again that synergies with your sacreds well. No-one will force you to take such a pretender though.

Now with blood - You'll still need earth (e1b3 is the suit in vanilla, can't remember if CBM modifies the values), You don't really need to invest to anything else than b3 on your pretender with e1, and the path isn't very useful for you for the rest of the game than simply few pebble skin suits just to replace the bloodstone economy it awarded before - the paths would effectively go to waste. Having b4 would grant a point or two of strength - while not useless, it's far from regen5 or whatever you'd be having with nature. In late game nature also awards you with GoRing wished sc's/summoned tartarians, which agartha nor (ma) ulm have no national access to. Granted - they neither do have high death mages (exception being la agartha and la ulm) or high-astral casters. MA Ulm could probably suit their SC need with Iron Angels, should they have the earth income. It's not the best chassis around, but it isn't too shabby either.

So. Should the pebble skin suit be made non-unique, it'd "hurt" the nations in comparison to the tome of gaia. Being cursed and turning the user into troll (not a very bad thing for ma ulm though), it'd see little use. Tome of Gaia is not cursed - it'd see probably more use, though the point to consider is if we would want another cheap earth booster, or something a bit more rare than the ubiquitious earth boots. Tome would also basically force them to have a pretender designed for it (whereas the suit doesn't explictly need it, but it very much hastens the process of making them), but it complements to their sacred units and/or mages. It also opens up the possibility of getting into race to gift of nature's bounty / oak / gift of health. For example, Nature's bounty is in enchantment, which I believe ma Agartha likes, and I don't see it as too bad a path for ulm either, with earth well in the end, and fire fend in the way.

Just points to consider. /ramble off