Creature design has always been tough for me. When I run tabletop games, I mostly use monsters out of the books. I can take credit for only a small number of the monsters in Dust to Dust. On the other hand, I've found that in almost every creative endeavor, the first few ideas are the tough ones; after that, ideas start to come more easily. Domain Sentinels are intended for use in the Aurikesh setting, but they work equally well in Birthright (this is not a coincidence) or any other setting made up of a patchwork of small countries, dukedoms, prince-bishoprics, and so on. Or even islands adrift in a sea of stars, if that's your thing...
This is the thing I haven't explained about Aurikesh yet, in all my posts about it. (Eventually I'll scan and post the map.) In deliberate imitation of the Birthright setting, the main land mass is divided up into fifteen domains, and each domain is made up of one or more of the forty-six provinces. I'd eventually like to apply Birthright's domain rules to these provinces, in case I ever have time to run such a game.
In trying to come up with a new creature for the setting, I naturally wanted to draw on the things in the setting that made it unique. Okay, unique-ish - I'm certainly up-front about the main source I'm stealing from! Well, if these provinces are so important, what is it that makes them that way? Were they always divided, even before the humans and kagandi arrived? Why is it that provinces change hands "whole," rather than just shifting borders by a few miles as happens in the real world? The game-running reason is obvious: because redrawing the map on that level would be a terrible pain in the ass, while noting that a province has changed hands is comparatively easy. I'd still like to have a compelling world reason that it works this way. I don't have that reason nailed down yet, but I felt that having golems directly tied to the domains (by some force that long predates the land's current owners) would reinforce the existence of that world rule. That is, it would prompt players to ask the question again, with a new piece of ambiguous evidence.
Unknown centuries - millennia? - before the humans and kagandi sailed from southerly Sestomera to Balioth, a now-presumed-lost race dwelt in Balioth and divided it among themselves, along the lines of provinces that persist in the present day. Ruins from that civilization are found in every province, and some of those ruins house constructs of stone, eight or nine feet tall. These constructs take many different shapes, according to the domain in which they are first found; in the northerly domain now called Pereil (or Atramyr's Crown, to the kagandi), the domain sentinels are like centaurs of stone, and one hand is a scythe-blade, and short horns sprout from their brows. In Dalassiria (Angel's Thorn, to the kagandi) - and only in Dalassiria - they have found domain sentinels with grotesquely over-sized claws and vents cut into the stone that spew flame.
Ambitious people, especially rulers and spellcasters, seek out domain sentinels so that they can be controlled by magic. The sentinels remain still and tolerate any amount of handling, inspection, and even transportation (if someone can figure out how to move a two-ton piece of irregularly-shaped stone), unless they are bound by a spellcaster who has learned the particular spells necessary. The only time a domain sentinel animates without an external, magical command is when the domain (as defined by the sentinel's original borders) faces an unmistakable existential threat, such as a catastrophic flood. At such times, the sentinels rouse themselves and attempt to intervene. Most of them fail to do so, as they are buried in long-forgotten ruins and frequently encased in rubble. Minor tremors of the earth that accompany other kinds of catastrophes are almost certainly domain sentinels struggling to reach the surface.
Domain sentinels are very strong and durable, although not limitlessly so. (I don't have 5e rules to help me write a stat block, but a single domain sentinel will be a considerable challenge for two characters of about seventh level.) Though made of stone, not all of them are clumsy or slow. Their specific capabilities vary predictably according to their shape; the centaur-like sentinels of Pereil can gallop as swiftly as a living horse, and do not tire. As long as they are not completely destroyed, a skilled stonemason can repair them with mortar or a spellcaster can repair them with magic. If they are completely destroyed, they cannot be restored to function by any known means. Destroyed sentinels are often used as statuary, either in crudely repaired form or in fragments.
Current estimates indicate that 150 or so domain sentinels have been found to date. Of those, twenty have been destroyed in combat, and twelve were deliberately destroyed by those who feared their use as weapons. The remaining sentinels are chiefly in the control of domain rulers or the wizards who serve them; it is highly illegal to control one except in service to the ruler of a domain (though Var Dyrak is reputed to control as many as eight). Curiously, the rulers of domains seem to receive the spell-like ability to compel sentinels when they are officially recognized in their office - a power that extends to the ruler's spouse if that spouse is legally regarded as a coequal ruler.
Many different groups commission explorers to seek out and retrieve domain sentinels. Of those, some are domain rulers looking to augment their military strength, some are spellcasters in search of a powerful bodyguard, and some are rebels against king and country who destroy the sentinels to keep them out of the hands of others. Any of these groups pay well enough to find plenty of recruits.
Very odd things happen when the most correct lawful rule of a province, or even a whole domain, is in question. When Saivel the Great made war against her neighbors and annexed a province from Eksoris, two of the domain servants controlled by Eksoris immediately stopped moving, and have never again stirred since that day, even when the province returned to its original control. At the same time, one domain servant controlled under Saivel's direct control suddenly spoke with a clear human voice, but in a language unknown to all present. It continued in this manner for three-quarters of an hour before it again fell silent, and it has not spoken again since that day despite powerful magical commands to do so.
Priests and lay scholars of Talend have given particularly thorough study to the domain sentinels, as there is clearly a powerful connection between these servitors and the concepts of sacred kingship that forms the foundation of their faith. To their disappointment, however, spellcasting priests of Talend have no greater or lesser ability to control domain sentinels than any other spellcaster.
The obvious sources of inspiration here include the Terracotta Army, the Shadow of the Colossus, Chinese guardian dogs, and gargoyles. When I eventually design their stats and means of control in detail, I'd like to work things out so that everyone once in awhile, it makes sense for the PCs to do... something... that controls the domain sentinels and sends them into battle (while the PCs themselves stay behind), more or less using the creatures as giant robots. At the same time, I want to make sure that isn't usually an optimal strategy for PCs, but is often useful for NPC villains. I'm not sure how I'll bring about that conflicting set of goals, but I'm open to suggestions.