3.0 What is the Golem Cult?
In short, the golem cult is +10% per level of friendly dominion, for your golems. This includes non-national golems such as Claymen and "Golem" golems. It does not cover undead. If I understand the system correctly, it remembers the highest province they stayed in, till getting damaged. It may pay to move new summons through a high dominion area on the way to the front. It WILL pay if you find any fast independents with magic leadership or twiceborn a oracle, since your map move is three, but all your default leaders are stuck at one.
3.1 Conjuration (Undead - death gems)
Awaken Cavern Wight (3 gems, summons one)
Consider it the poor man's Wight, it available at the same time as the regular Wight, but at DE, not DD. It also costs 40% less gems. It loses the Bane Blade, but it gains a higher damage Glaive. It gains more hitpoints, but loses a lot of protection. In general, it is inferior. Still, it is a fairly tough unit for the cost, and that chill affect can come in quite handy. Remember, chill stacks, and every 20/10 points reduces enemy attack/defense. Every 15 increases the chance for critical hits. You might freeze them, also.
Summon Umbral (2 gems, summons one)
A very impressive stealthy, ethereal, life draining unit. Like all ethereal units, it is vulnerable to magical weapons, but with a meaty 68 hitpoints, it isn't going to be threatened by any old banishment prayer. It is a lot harder to mass than shades, being only one to a spell, but you won't have much undead leadership capacity anyways. it's quite strong, has solid attack, morale, and defense, and a pretty good MR of 16.
While they are worth including in a standard force, keep in mind the Rod of the Leper King (1D). This can give any of your units, even the scout, fifty undead leadership. The disease is a downside, but if you managed to summon a Black Servant (2D), you can avoid that problem and have yourself a stealthy raiding force. If you can't do that, they're still worth using. In short, I'd say ambushes.
Sun Tzu's Art of War has some vague, but interesting things to say with regards to this. It's a pretty short read, I highly recommend it.
3.2 Enchantment (Golems - earth gems)
Your golems are the centerpiece of your Agarthan strategy. You can mix things up quite a bit, but you'll use golems or lose. They are magical beings, lifeless, inanimate, mindless, and neverhealing - outside of labs, that is. They have 50 morale, 22 protection, and 0 encumbrance. All that grants certain immunities and advantages, but leads to a few weaknesses you'll have to learn about.
They a nice map move of three, but unfortunately you're limited to map-move 1 magic leaders. If you find a fast independent mage or twiceborn an oracle, that will be a big help.
Quite a few are sacred. I'll cover blesses in a later section. I will briefly mention that earth and nature blesses are just about moot w/regards to golems.
They don't take much damage, but when they do, you'll need to retreat/ferry a few to the nearest lab. However, since they can only be led by a mage, you can build your own. They can carry the bonus hitpoints they get from a friendly dominion into a hostile dominion.
While I've brought up the subject of their leadership, the one greatest threat to your golems is going without. If you have no mages present on the battlefield, your golems instagib. That is, they burst into a horrifying cloud of blood. The total amount of magic leadership doesn't matter, however, as long as there is some there. You'll need to protect your mages and factor in redundancy. Bodyguards will help deal with arrows and flyers, but aren't perfect. Stoneskin helps, but can't be depended on, since DRN is an open-ended roll, and fatigue increases the chances of criticals. Your mages won't die in every combat, they're not at risk, but you'll curse yourself when you forget bodyguards, and two lucky arrows deal ten points of damage to your two stoneskinned golem crafters and slay all your golems. It's almost always better to err on the side of caution when dealing with golem leaders. Failure isn't that common, but it is catastrophic when it occurs.
To repeat, to prevent the catastrophic loss of all your golems, all you typically need is a little protection, a few (human) bodyguards, and a little redundancy. Even imperfect as it is, stoneskin is well worth casting. Oh, and don't bunch your mages up. There will be situations later on where you need to take extraordinary measures, but those will usually be self evident. It's rather convenient that water/earth offers both Resist Fire and Cold Resistance. And with a Dwarven Hammer, certain trinkets only cost 3 gems. Lightning Rod, Ring of Fire/Frost. And if you're desperate, the Lead Shield is always available, but a bit pricy.
Most of your golems are sacred, opening some opportunites, wear no armor (all natural protection, important to know), and have a patrol bonus, helping you to raise money in a pinch.
Attentive Statues (4 gems, summons two)
It's easy to overlook these units with the much more attractive Enliven Sentinels just around the corner, but you're doing yourself a great disservice by doing so. By cutting off your research goal at t3, you allow yourself a lot more flexibility with your early commanders. Even with a dominion of 1, these are a force to be feared. I once had twelve of them take on a Mictlan army of 70, and win. One casualty. One. There were a few gaping chest wounds, but those were inconsequential and an inevitable result of being so grossly outnumbered and unsupported. I admit, it was against the AI, but I was still quite impressed.
Unlike your later nationals, these guys lack sacred, come with Stone Shields (manual is incorrect), and have a defense value of 14. They will still benefit from your dominion, so that helps compensate for their relatively low health. I say relatively, because for humanoid infantry, they've got above average hitpoints, strength, attack, defense, mr. And obscene morale & protection. They'll tear through undead and heavy infantry. Crossbows will hardly bother them. Even with armor piercing, they've got 11 prot. left and a good shield with a high parry value. High strength units may cause problems, but by high strength, I mean giant level, not berserked barbarians.
Enliven Sentinel (4 gems, summons one)
Once you start encountering tougher resistance, you'll switch to these. These and all further units lack shields, or the excellent defense. But, the boost in hitpoints means they'll last longer without repairs, will get less wounds, and benefit more from your dominion. They're size three, so they're still capable of outnumbering a giant or pretender. In addition to the obvious boost from strength, they get an additional damage boost from their Granite Glaive. And they're the highest you can summon without boosters or oracles. That's quite important sometimes. Don't forget to now take advantage of any national blesses you might have, and take them to labs for occasional repair.
Enliven Granite Guard (12 gems, summons one)
These are expensive, requiring 12 earth gems and an 400 gold Oracle of the Ancients (or Earth Boots golem crafter) to summon. What you get is a MEAN UNIT, that you'll definetly want to deploy to any checkpoints or bring to your critical battles. If you have any dom10 provinces, you get a whopping 150 hitpoints, that even the King of Deeper Earth can't beat. Their only fundamental problem is overkill. They can be a waste of gems that way.
Enliven Marble Oracle (45 gems, summons one)
Unfortunately, this commander gets no leadership without artifacts. Fortunately, you can equip this marble nudist with a full range of artifacts. Holy two is on occasion nice, but for real fun, and over 300 hitpoints, prophetize him. As icing on the cake, you'll get the strength bonuses, MR dominion bonus, attack and defense bonus bonus, and a permanent bless.
Special Golem Threats:
Disrepair. Nations with common earth mages. Having all your mages die off and insta-gib your golems. Armor negating spells threaten everyone, but your golem's less so, thanks to bountiful hitpoints. Your greatest threat will probably be generated by other nations with earth magic. Shatter is harmful, but less so once you get 100+ hitpoint Granite Guardians. Earth forging gives nations access to Smasher (e2), which does extra damage to inanimates and undead. IT makes available plenty of armor piercing/negating weapons. Air nations have easy access to the Thunder Whip (A1), with Armor Negating. Etcetera. However, the only thing you really need worry about all the time is any tactics hitting your mages. They are your weakest link.
Odds and ends:
Various units such as Clay Men also get the dominion bonus. If you think any non-national golem deserves a mention, tell me and I'll edit it in here. Other comments, too.