Thanks

I appreciate the thorough critique.
Yeah, I like immortal pretenders, and liches in general. I felt like there should be one immortal undead dragon somewhere. It's pretty badly suited for a rainbow, but the death 9 bless on the two sacred mages can be pretty good for some of the broader area spells like bladewind, and give the sacred summon a little extra kick against strong/healthy summons.
Well, um Rangers don't have a pillage bonus. Rangers only have waste survival, +10 stealth, and a patrol bonus on top of a regular kobold. The patrol bonus was added for thematic purposes (kobolds are paranoid and constantly patrol their territory) but gameplay-wise is useful for MP play if anyone is so inclined, so you can prevent stealth preachers/scouts/spies on the cheap. It's pretty synergistic with the good province defense of Urdheim.
As spies AND stealthy leaders (for leading raiding parties) AND possessing the net trap (which makes them somewhat useful assisting kobold armies even without a magic weapon equipped), I feel they should be somewhat pricey compared to most basic commanders. Even removing the patrol bonus would only probably drop the price by maybe 10 gold?
That's kind of the style of the kobolds, even though most of them are rather useless and weak, because there's just so many, they have more exceptional individuals. Those come at a premium, but make the kobold nation survive/viable when compared to others, and so interesting (at least, to me).
The Raiders have a pillage bonus, which is also somewhat thematic. I doubt any human would really use the pillage option, but if they so desired, they're a good group to do so with. The raider farsummon could eventually be used in that sense. Farsummon 4/5 groups of them into poorly defended back-provinces which you've scried upon, and then set them all to pillage, even if the opponent has a defense force sitting next to it, they could only stop one of them at a time.
(Even though I'm not a hardcore MP player, I tried to make Urdheim a viable/good nation to use in a MP game)
The firebrands are kind of a niche unit. Useful against Neifels/Vans or whenever else you need aoe 1 fire attacks, but too fragile and expensive to rely upon significantly.
The flying strike force is pretty solid. It's also a good idea to use one 4fire glaurung for a prophet to lead the sacred summons (at least, if you have more firegems than you're using, and generally I send one glaurung to site search behind my conventional kobold army to make sure I do).
The summoners are a kind of long-range artillery, though too expensive to really throw around. It should be relatively useful to use in a more defensive game though, as attacking a province which has summoners on top of province defense should be rather painful. (Though you may never see them outside a fort)
The different mages each have their own strength/weakness to make each of them viable. The blessed are of course your cheapest priest, but they also have a supply bonus aside from what the nature randoms get, which can make them somewhat useful throughout the game, particularly if you rely on large kobold armies, (even more so in unpleasant enemy dominions). Though they are more than twice as expensive as the waterborn, they're still a reasonable researcher option because of being sacred, and having a small chance at 2W or 2N (should be 10%). The waterborn can be made in any fort without a lab or temple, and that's their strength. Amphibious on both of them is pretty significant if you stumble on a shambler/kappa province early.
The Sorcerors have different national spells available to them depending on the random they get. So you'll have fire trappers, ambushers, castigators, and defensive buffers, in addition to the usual magic (such as fireballs or skelespam).
I've strengthened the Earth Scion a bit with a siegebonus to broaden it out from being a specialty thug/forger, to also being somewhat more useful as an army supporter. (Kobolds low strength means you need very large amounts of kobolds to siege anything, usually about 2-3 for each normal human, which makes miners pretty necessary. The Scion now can be a bit of a viable alternative to needing sizeable miner squads. Yes, I've thought about giving a siegebonus 1 to the kobolds early in the mods development, but I like the idea of having very large kobold forces to take over fortresses, or the need to sap enemy walls (use miners).)
Yeah, all of the kobold units are rather fragile, even the more expensive firebreather and the flyer. Battlemage squads should be the alternative against cav/tramplers.
Well, the dragonstone is an immobile pretender. It's there mostly for style/thematic purposes (and to give players more options yet keep things Kobold-like, like KO I like more options too even if they're rarely used), though it's also viable for fire/earth bless (such as E9/F4, and yes I realize fire/earth is somewhat suboptimal both as a bless, and with Urdheim already having plenty of fire/earth mages.). I've played a couple games with f4/e4/d4/n4 dragonstone and the sacred summons are reasonably potent/durable with that bless, though you're rather limited in how many of them you can mass. This probably won't come up, but the dragonstone should be incredibly tough to take out in the capital (in case of MP play, and anxiety of early bless rush).
Anyway, glad you like it.
So I guess I have some questions for you (and anyone else too, don't be shy):
1a. Have you tried v.20?
1b. Do you like the changes?
1c. Have you gotten the new villain (hero) yet?

2a. Do you feel any unit/spell is too strong/weak? Is there something that seems useless (not necessarily unwanted for your style but just useless overall)?
2b. Anything that needs to be done to achieve vanilla balance (as compared to an above average vanilla nation)?
3. Any miscellaneous things you'd like to see? Or random other suggestions?
To everyone:
There's still some stuff I may or may not add to Urdheim, possibly another hero or pretender (btw, I'm really open to ideas), but it's mostly just balancing. If the next Dominions 3 patch changes anything significantly or opens up some new mod commands that may warrant going back and updating everything as well.