(Note that this is based on the assumption that Prospit and Derse have a “bottomless history”; if you argue that they sprang into existence 13 or 39 or whatever years ago, some of this won’t work.)

POLITICAL: Prospit and Derse are both monarchies - with the sole theoretical power vested in the King and Queen. However, most of the ruling of civilians is done Queenside, and most of that ruling is done indirectly. We already know Derse’s solution: a sprawling bureaucracy of Agents in which every organ has strictly delineated powers, all answerable to an Archagent. The personal details of the Archangent’s relationship with the Queen are not general knowledge, but the fact that they do work closely is known; Jack is the Queen’s Own Agent in everyday affairs, and his power over the bureaucracy flows from that entanglement as much as from his own strongman tendencies.

And I think this is probably pretty similar to the Prospit model - the idea of a strictly delineated bureaucracy sort of fits the “idea” of a kingdom of chessmen. I think there’s probably differences in how the model plays out - the personal relationship between the white Archagent and Queen is probably very different from the clinging, scraping hate of Jack and BQ - but the structure is likely the same.

ECONOMIC: While the economic systems of the Light and Dark Kingdoms are supposedly free, there’s a cultural expectation that a citizen will find their calling long before the war begins, and stick with it. Switching from job to job is unusual, and generally brings down a stigma of having a job of “drifter” or “temp” instead of any of the callings in question. Added to this is the strong role of the government in the public sector - most industries have a royal presence, especially ones that involve interplanetary commerce.

Prospit’s main strength in the war is the abundance of its physical goods. In low orbit around Prospit and in spitting distance from the Lands, it has close access to food and materials, and a healthy import/export industry (dominated by official Royal Navy operations) exists to supply the Light Planet with the abundance that is its namesake. Derse has more problems here, and the reason is pretty simple: they’re about as far from Skaia as they can be, and are separated from the Medium by the difficult-to-navigate Veil. They still farm on the Battlefield, but shipping the goods from the serfs to Derse is a costly affair. Before the war heats up, the Royal Navy is the only “official” supplier of food to the dark planet, but in reality it competes with various black market outfits that source their supplies from the Battlefield or Prospit (a good number of them secretly in the pocket of the Archagent). When the war effort begins in earnest and the Navy’s resources become split between shipping in food and shipping out troops, these black market sources begin to be the primary supplier of food to the citizenry at large.

IDEOLOGICAL: The primary ideological stage of the Incipisphere is the matter of Skaia and the cycle of rebirth that it represents. Two major philosophies dominate here. One, held by the King and Queen (and most citizens) of Prospit, is that growth is necessary, even growth of ephemeral things. That universes giving birth to universes giving birth to universes is a thing holy and beautiful. Hence, the establishment of Prospit fights to protect Skaia until it can come to bloom. The Dersite establishment, in contrast, sees unrestrained growth as a cancer upon the world - it’s better to live in the immortal steady states that Prospit and Derse themselves represent than to grow without bound, strangle out other life, and eventually rot and die regardless. This ideological divide, more than duress of the crown or economic concerns, is the primary motivating factor for the war, and the royalty generally use the full power available to them to prevent the other’s philosophy from taking root in their kingdom. Derse’s outlawing of frog icons is well-known, but Prospit suppresses veneration of the Horrorterrors equally vehemently, in no small part because a theoretical Prospitian double agent would have such easy access to Skaia (and thus could theoretically threaten its ability to play host to the Genesis Frog).

Interwoven with this is the philosophy of a sort of “divine right” of the royalty to rule. Prospit and Derse both venerate the symbols which will one day enter the prototype towers as embodiments of the Power of the King; the crown, and the regalia (which save or doom Skaia) and the prototype symbols are all interwoven, all equally sacred. This is held to various degrees by individuals, and is far less enforced than the cult of Bilious Slick or that of the Horrorterrors (certainly, Jack and WV are two examples of people who openly hold the royalty in disregard).

MILITARY: Whatever the ideological power backing the monarchy, it has some significant “real” muscle behind it: the Ring and Scepter, doomsday weapons in their own right. It’s the threat by which Prospit and Derse proper can successfully stay out of the war. It’s the power by which the King remains King, and avoids all but the most extraordinary mutinies, and leads his side’s forces on the Battlefield, bolstered on the White side by superior supply chains, and the Black side by superior access to Veil technology.

Derse has an additional advantage in this area, however: their access to the Veil allows them to manufacture Underlings in addition to their vat-grown Battlefield soldiers, which give them a sort of indirect military control of the Medium. Hence their ability to enforce their laws there - their successful restriction of Pondsquatter idols as “contraband” is one example - whereas Prospit’s sphere of influence seems to be limited to the Battlefield and the Golden City only.

TECHNICAL: This is the category in which the individual carapace shines. Over the course of the years and centuries in which they settle into their roles, they acquire an incredible depth of specialist knowledge in whatever their field might be. If a Parcel Mistress has a significantly important parcel to deliver, even the Queen on her throne must yield. Especially notable among these are the villeins who tend the food on the Battlefield, and the technicians working the machinery in the Veil - people whose specialist knowledge is singularly vital to the war effort. Nor should the King and Queen be left out of this category; they’ve trained as much as anyone else to fill their role, and Jack’s disastrous rampage across the Incipisphere is an excellent example of why an understanding of the game is necessary to rule. Remember: if the White Queen hadn’t abdicated, Jack would have been shot out of the Prospitian sky.