La Guerre des Marques was a terrible and bloody conflict which changeld the face of Khorvaire, solidifying the Maisons Marquées Du Dragon' position today.

The war began about five hundred years before the establishment of Galifar, when the Maisons Marquées Du Dragon launched an inquisition to put an end to the proliferation of aberrant and mixed Dracomarques.

The houses had the advantage of greater numbers, but the aberrant marks of the time carried tremendous destructive power. In the third year of the war, Lord Halas Tarkanan began organizing his aberrant kindred into a proper military force to oppose the Maisons Marquées Du Dragon. Tarkanan, known as “The Earthshaker”, carried an aberrant mark that gave him great control over the Élémentaire forces of earth and fire.

However, Tarkanan's main contribution to La Guerre des Marques was his brilliance in tactics and strategy. His consort, the Lady of Plague, was an enigmatic woman whose Marque Du Dragon power was never specified, but her title and the end of the war suggests that it allowed her to call upon a multitude of small creatures and deadly plagues.

Although Tarkanan's efforts extended the conflict, the aberrants fell in the end. Tarkanan himself was trapped in the siege of Sharn, which had been his stronghold and base of operations. When it became clear that the aberrants were doomed, he and the Lady of Plague unleashed the full power of their marks - power sufficient to destroy the city. Terrible quakes caused the collapse of parts of the city, and rivers of lava flowed up from the fiery lakes below. Masses of pests and horrible plagues ravaged invaders and defenders alike. Some claim that the Lady of Plague's death-curse still lingers in the depths of Sharn.

La Guerre des Marques ultimately established the Marqué par le Dragon families that hold power today, and it laid the foundation for the prominent role of both Maison Bombardier and Maison Garda, which played central roles in La Dernière Guerre. It also led to the foundation of the Twelve as an avenue for the houses to cooperate toward Commun aims.

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Though Karrn failed in his conquest, his wars helped raise awareness of the Marqué par le Dragon as his soldiers traveled to distant lands. Over the next few centuries, the families began to communicate with one another, with the leaders of Siri and Bombardier taking the greatest initiative. However, it would take a second war to truly bring the families together and forge the foundation of the modern system of houses.
In the present day, few truths survive from La Guerre des Marques. History is written by the victors, and the Maisons Marquées Du Dragon have had fifteen hundred years to codify the persecution of the aberrants. What remain are superstitions and folktales: myths of aberrant monsters whose power could shatter cities. Many aberrants were said to be driven mad by the power of their marks—children of Khyber, touched by darkness. Those who bore the true marks were champions blessed by Siberys, or so the Marqué par le Dragon claimed. All that is truly known is that the Marque Aberrante du Dragon of old were not bound by bloodline, and that they were as unpredictable as they were powerful.
Some say the fledgling Maisons Marquées Du Dragon saw a purge of the aberrants as the means to ensure their mystical monopoly. Others believe that the threat of the aberrants was inflated to force the Marqué par le Dragon families together. A few sages have suggested that the entire war and its aftermath were the work of the dragons of Argonnessen: that the creation of the houses served the Prophecy, and that the Marqué par le Dragon have always been unwitting tools of these ancient wyrms.
Some of the heroes and events of La Guerre des Marques are discussed in Chapter 4 and in the Sharn: Cité des Tours supplement. Alliances were forged in the heat of battle, and in the aftermath of the conflict, the leaders of the young houses formed the council of Les Douzes. This arcane cabal established the unifying traditions of the Marqué par le Dragon, and set the standards by which the houses are governed to this day.

Source: Marqué par le Dragon