Answer: The words and sigil of House Thrax give immediate insight into the nature of the house and its nobles. After all, how can "Tears in our wake, never at our wake" with a house sigil of a blood-red wake widening behind a sea serpent leave any doubt to a great noble house's intentions? House Thrax has been the dominant naval force of Arvum for the better part of a thousand years and are unlikely to let any of the other great houses ever forget it. Unapologetically militant, ambitious, and scorning the kinder aspects of chivalry, House Thrax has relatively few annointed knights, though their military successes have not suffered for it.
The only house without land holdings on Arvum proper, House Thrax and the bulk of its vassals are spread among the many islands of the Mourning Isles, in the eastern sea between Arvum and Eurus. Their dominance at sea and lack of assailable cities by land has enabled them to cling easily to traditions that have been rejected by the Compact as a whole- they are the only great house to still follow strict male primogeniture, and despite the Compact firmly outlawing slavery, their system of thralldom is viewed by the other houses as slavery in all but name, with scant few prisoners taken in raids and war ever given the chance to purchase their freedom.
The bloodstained, savage and antagonistic reputation of House Thrax does not come without significant costs, however. They are possibly the most reviled of the great houses, and have on at least three occasions lost wars against House Grayson and its allies over questions of succession of the monarchy. Nor are all the foes of House Thrax external- the loyalties of many of their vassal houses are far from certain, they are often plagued by pirates made up of escaped thralls, and their fondness for trial by combat has created difficulties in their own internal succession crises more than once. Nonetheless, few coastal towns or ships fail to feel trepidation at seeing the sails of House Thrax.
Terrors of the waves, many of their enemies have long denigrated House Thrax with insulting names, but the sobriquet of 'Sea Serpents' sees widespread use even among their lands.
Answer: "Say what they will about them, but House Thrax and all of the Mourning Isles are loyal. They are loyal to their traditions. They are loyal to their houses. They are loyal to their families. They are loyal to institutions greater than any individual, and they view it as the height of arrogance for any person to put themselves above the institutions that have long seen to the Mourning Isles' survival. They believe in a strict order that the lower serves the higher, from thrall to debt holder, to commoner to noble, to noble to ruling lord, from ruling lord to house. Anyone can and will be sacrificed to preserve the house, for the house owes an individual nothing." - Archduchess Carlotta Velenosa, 'Commentaries on Thrax'
"Our traditions are the walls of Maelstrom that have stood against every attack for a thousand years. Our traditions are the shepherds that guide flocks of sheep as the wolves howl and hunt. Our traditions are the bedrock foundations that stop us from tumbling into the sea. We forget them at our peril." - Prince Donerian Thrax
Far and away the most traditional of the five great houses, a Thraxian can never go much wrong with actions that show respect and loyalty to the institutions of their birth. Any Arvani that takes an action defending an institution again change is likely to get Thraxian approval, who generally have the stance that if it ain't broke, don't fix it, and if it is broke then have some reverence to the broken institution and don't go poking at it. Change when it comes will almost never be welcome, and any interlopers bearing change will find cold welcome for at least a few generations until the good old days fade from living memory. Moreover, most of the Mourning Isles tend to be reactionary- if something is changed, they very much would like to see it reverted, before it's too late and a valuable institution is forever lost.
To win support in the Isles, nobles typically have to present themselves as defending an institution, protecting the status quo, or restoring a weakened institution to its rightful place. In the Assembly of Peers, it's common for peers trying to win Islander support to constantly reference historical figures or precedents that would support a course of action, or frame the desired outcome as minimizing threats to institutions.
Exemplar: Most of the Princes of Maelstrom have been presented as the core defender of the Thraxian way of life in the Mourning Isles, and a number have embodied that. Defending traditions to Thrax means protecting thralldom as an institution, respecting the gender norms they've established, all the privileges of the peerage, and traditional respect for house honor and its dignity. As an example of defending the house's name, Prince Drake Thrax, the father of Donrai, famously had his own brother and closest friend executed for oathbreaking and disrespecting Thrax traditions when the other man accidentally killed a guest during a feast at Maelstrom as the result of a drunken quarrel. Violating guest right was not a stain Thrax was willing to endure upon its honor.
The Worst: Even to this day, King Alarius Grayson is widely reviled in the Mourning Isles several hundred years after his death. As the largest defenders of tradition and the house that most deeply respects authority, House Thrax was an unlikely leaders of the coup that started the Crownbreaker Wars, and it is certain that Thrax would never have had the support of its people to start the war were it not for the devastatingly effective propaganda campaign that unfairly painted King Alarius Grayson as a figure trying to destroy Islander traditions. Early into his reign, King Alarius Grayson briefly proposed trying to establish a unified code of law that would stretch across the Compact in order to ensure fairness and consistency in punishments. This horrified many peers that traditionally guard their authority in their own domains, and the proposal was quickly dropped, but an unrelenting propaganda campaign followed that painted every action by Alarius as having overtones of seeking to destroy traditions such as thralldom and more general noble protections of their status. In one telling example, to help alleviate some of the workload of Crown Magistrates, he established a Commoners Assembly to address minor concerns, which in turn became wild rumors that he was going to try to disband the peerage and create a republic. Many of the seraphs in the Mourning Isles in the few years leading up to the start of the Crownbreaker Wars were suspiciously new appointments, who preached on the importance of tradition and its role in maintaining stability and were deeply critical of Alarius, and more wild rumors followed that continuously undermined his legitimacy, and suggested that Prince William Thrax, due to his close bloodline, was actually closer in line to the Throne. By the time of King Alarius' death, he was presented as the greatest threat to tradition Thrax had ever seen, and most of the Mourning Isle peers were demanding something to be done about the man that had absolutely no idea any of this was occurring.
Political Allies and Adversaries: When it comes to tradition, Thrax usually seeks to pragmatically appeal to the entrenched institutions that would have any change undermine existing authority or power. Any change that would ever diminish the authority of the peerage in any way usually has Thrax shoring up support among all the peers, and Thrax works best with other houses whenever an institution is under attack, often being allies of House Valardin when it comes to supporting the Faith's authority. The Lyceum is often a wild card in pragmatically supporting or undermining an institution as it suits their needs, while Redrain is most often to ignore a tradition that it thinks is dated, unnecessary, and 'dumb'. Grayson often emphasizes the power of the Crown, but beyond that is far too egalitarian for Thraxian tastes.
--House Before Self--
"I have no son. And you, stranger, are trespassing on my land." --- Traditional Thrax farewell to a son who has shamed the family
Many Thrax stories tell of their heroes valiantly sacrificing themselves for the betterment of their houses, but that doesn't really reflect the true ruthlessness of Mourning Islander houses in their willingness to sacrifice members. No great house comes anywhere close to the number of nobles stripped of their nobility as the Mourning Isles. By virtue of their birth, any noble is presumed to be competent and worthy of their house, and if they ever prove otherwise by failure, it is a simple matter to discard them. Entire sellsword companies have been made up of discarded nobility from the Mourning Isles, and Thraxian families tend to be quite large with the knowledge that at least a few of the spares will probably prove themselves unworthy of their bloodline. Selfishness at the expense of their houses, and ambition that damage their houses, or creating an embarrassment for their houses, is devastating to any Thrax noble. The fortunate might have proven useful enough to get a second chance, but many are not near that lucky.
No great house respects bloodlines as much as Thrax does, which also means that neonobles tend to be the rarest and least welcome in the Mourning Isles. In fact, it is common place that any commoner raised to nobility in Thrax is assumed to have some noble blood in them, and it is unheard of for a commoner to be ennobled without at least a polite fiction suggesting they were at least distantly related to nobility.
With their great fear of bringing shame to their house and being cast out as a result, Thraxians tend to be very formal, courteous and fastidious. There is very little improvisation or risky jokes in their family meetings as a rule, with exquisitely kept politeness to avoid being the one that appears to take the family honor less seriously than the others. The utter ruthlessness in family heads disowning heirs is so widespread that it's a popular trope in plays in the Compact to have a lower born Thraxian noble turn to a Lycene ally in a plot to remove those in front of them as heir, using blackmail or embarrassment.
Exemplar: House before self, and the ideal many Thraxians aspire to is someone who works tirelessly to advance their house and leaves it vastly stronger. Princess Marie Thrax was such an example, and one of the root causes for House Thrax's women being utterly dominant in law and scholarly pursuits in the Isles. While in very recent times the Mourning Isles have started easing their gender restrictions to mirror the rest of the Compact, the tradition of law and scholarly pursuits being women's work still largely persists in the Isles, and its roots come from this very early historical figure back in the far past when male primogeniture was common throughout the Compact, hundreds of years before Queen Alarice the Great shattered barriers through the Compact and forever changed society in the wake of the Elven War. Sister of a mostly forgotten highlord in the last times several centuries after the Reckoning, Marie was a self-taught brilliant legal scholar who routinely untangled disputes between vassal houses of Thrax, and was said to have prevented scores of conflicts from growing into wars through her arbitration, consistently leaving Thrax in a better position. She worked with the Faith of the Pantheon, and encouraged every idle noble not going to war to work heavily with the scholars of Vellichor, which lead to the Isles having a strongly disproportionate representation in the very early Crown courts. While it's mostly forgotten in modern times, a large percentage of Archscholars of Vellichor were Thraxian women, as were a majority of the chief magistrates of Arx, and most of the precedents used in resolving trade and border disputes between houses came as a direct result of Princess Marie Thrax and her followers arbitration.
The Worst: One of the greatest insults that someone can offer a Thraxian without realizing the gravity of the situation is to joke about someone who drowned. One never, ever mocks Islanders that die from drowning, and great respect is given in the Isles to the departed. The odd sensitivity is from an unspoken custom in the Mourning Isles that few outside realize; when a child dishonors their house and is in danger of being disowned, many spare their house the shame by walking into the sea and drowning themselves. 'Walking into the sea' is rarely spoken of, but most Thraxian heirs have heard of at least one other that put on full ceremonial plate armor that they hope to still be wearing in the Shining Lands, and jumped off a ship or just marched into the waves and drowned themselves. Of course, not all do, and a few even fake their deaths or mock the custom. The Undrowned Sons are a much reviled, much hated group of pirates made entirely from disowned offspring of noble houses, known for piratical raids on Thrax shipping and having gone outlaw. A sometimes sellsail company that no Thraxian house would ever do business with, they are used as an example of the worst of the worst that comes from the Mourning Isles.
--Pragmatic, Disciplined, Calculating, and (surprisingly) Forgiving--
Despite that reverence for their traditions and institutions, House Thrax is not very idealistic, and has a pragmatism second only to the Lyceum when it comes to achieving their goals. They don't tend to hold grudges, and Thraxians that are selfish enough to let a personal quarrel get in the way of serving the house are condemned. Extraordinarily disciplined, individuals seeking personal glory at the expense of the house are seen as selfish and dangerous, so the heroes of Thrax tend to be presented in stories as surpassing what was expected of them, never bucking authority and never going against orders. While the ideals of the Pantheon are to be respected, they always come secondary to a pragmatic approach to approving the well being of their house, and most of the aspirational nature of the Faith of the Pantheon is more about avoiding condemnation that could bring dishonor to their house.
-Grayson: Completely wrong headed. It's the responsibility of the vassals to serve the house, not the house to serve the people.
-Redrain: Pragmatic and they don't hold grudges, but they have no respect for institutions and are completely undisciplined.
-Valardin: Have a good respect for traditions and are disciplined, but let personal honor get in the way.
-Lyceum: Their pragmatism is refreshing and they are strong allies, but they need to respect institutions more.
Answer: Slavery has been officially outlawed throughout the entire Compact of Arvum for nearly eight hundred years, and the practive has vanished from every great house. Except, arguably, House Thrax. The practice of Thralldom is a system of indentured servitude that has evolved over generations into something darker. Thralls that should have been serving short sentences instead saw not only their lives, but the lives of their children claimed by an ever increasing and often arbitrary debt. Criminals and prisoners of war were the typical candidates for Thralldom, and it remains a possible punishment today.
In 1006 AR Highlord Victus Thrax came to power. With the aid of Octavia Kennex, he had new laws on Thralldom drafted and put into effect. These laws greatly curtailed the exploitive practices that had become common to Thralldom (See help Thrall Laws). This resulted in the number of new thralls being made dropping precipitously. Within the year House Kennex made the decision to abolished Thralldom entirely within their holdings, generous donations from the faith and across the compact allowing them to weather the economic impact.
Thralls still remain by the millions. Those in Maelstrom and Arx are being given better treatment in line with servants, but that is just a fraction of those thralls still out there. How well the various fealties beyond Kennex will honor the new rules Thrax has placed on their Thralls remains to be seen.