The Martyr Compact was an attempt by the dragon emperors to maintain their empire in the face of a three way war with the dwarves and the elves. They hoped that with the sacrifice of a clan, the humanoids would be too weakened to want to continue the war. In that respect they were right. However, the dragons were too vain and way too proud to ever consider sacrificing an entire clan to the Pit. So they hatched a plan of their own. While the dwarven and elven kingdom sacrificed the steel dwarves and sky elves respectively, the dragon arrived with four hundred dragons of varying colors and sizes. It was only when the spell that opened a portal to the Pit, and that infernal magic clashed with the magic of the draconic, dwarven, and elven casters that the dragon emperors trick was revealed. Instead of healthy dragons, the emperors had scoured the land for all the deeply wounded, and nearly dying dragons. Magic had made them look healthy and strong. The spell was finished, and all three groups vanished. The dragons left the gawking elves and dwarves, arguing that even a wounded dragon was worth more than a company of either race. They thought nothing of the sacrificed dragons. They should have.
The dragons, having arrived in the Pit were immediately set upon by the infernal races. Even wounded however, these were dragons. Demons, and devils alike fell by the score, and the only casualties among the dragons, were those that had been already dying. The infernal races and creatures quickly learned to give the dragons a wide berth. The dragons, began to stake territories, claiming a large section of the Twisted Plains for their own. They stayed close together, something altogether not dragon like, for mutual protection. They needn’t have bothered.
Dragons are highly magical creatures. Part of the magic allows them to adapt and even manipulate their environment. That same magic is what allows them to crossbreed with virtually any living creature, creating a half-dragon offspring of the non draconic parent. Both of these qualities served to ensure the dragons survival. Like any other living creature, dragons need to eat. And the infernal denizens of the Pit were in plentiful supply.
The continual feed on the infernal races, imbued with the hellish magic of the Pit affected the dragons. They quickly began to heal, and manifest powers. They discovered by consuming a creature from the Pit (and eventually beyond it), they could add its power to their own. The dragons then began hunting the demons and devils in earnest, their lust for power once again reaching true draconic proportions. They had become Protean Dragons, powerful wyrms capable of countless evolutions.
Even death is horrific. When a protean dragon dies, it explodes and a number of wrymlings, named whelplings emerge from the remains. Protean whelplings look like miniature grey dragons. Their scales take on the colors of those they eat. The faster whelplings either flee, or immediately attack their brethren, depending on whether or not what killed their parent is still in the vicinity.
The worst was yet to come.
Ix’thaal a powerful blue dragon had fought and killed a demon lord. Consuming the demon lord had transformed Ix’thaal into a demon lord himself. To assert his power, Ix’thaal tracked down and killed his rival, a red dragon. Upon consuming him, Ix’thaal apotheosized into a monstrous version of himself. He had doubled in size and power. His breath weapon was a thing of pure destruction, a focused blast of pure energy, capable of cutting through anything in its path. His scales had become purple and black, though a crown of blue scales above his eyes still linger. Ix’thaal named this new form, becoming the first abyssal dragon.
It is this form all Protean dragon seek. Due to this, all Protean dragons intensely distrust each other, and are no longer willing to work together. Thus in the Pit, dragon lairs are miles away from any other dragon. It should be noted that like the ash dwarves, and rune elves, protean dragons seek revenge on the dragon emperors, and on the rest of dragonkind. The only time they will work together is in this endeavor. Fortunately that is a rare occurrence. They will work with ash dwarves and rune elves, as the two races have routine outings on the Material Plane.
A side note, a whelpling who consumes another whelpling does not become an abyssal dragon, or abyssal whelping. It is believed because the whelpling has not consumed enough infernal matter to induce apotheosis. Curiously, a whelpling who manages to consume a young dragon, protean or not, does become an abyssal dragon, albeit smaller than an adult who consumes another adult or ancient dragon.
A Darkness Rising 