The Gratechosen

Orvech was profoundly disturbed. It was the talk of every clan, the gossip in every hovel town. "A new Gratechosen has been found!" they said. Orvech knew better.
Certainly, such a claim had not been made in this generation, not since the great Antilla Spearsong had fallen in battle. But Orvech had been there, by Antilla's side, when she had breathed her last. Orvech knew, somehow, that she would be the last of the Chosen Ones. He didn't know how he knew, but he had felt it. Felt it in his bones. Like a breath of piercing wind, like a knife through his very soul.
No. In great surety, there would never be another Gratechosen.
And that meant that this new, so-called "Chosen" was an imposter.
Maybe Orvech would answer the call after all.

Loyalty over Grudges

Orcs are proud, savage, and violent, and so is their culture. They show no mercy to their enemies, have no care for negotiations, political movements, or the pandering of lesser races. If you have offended an orc, you have offended their entire kin.
Such volatility in a society, a culture, and entire race, means that that race is ever prone to infighting. The orcs are no exception.
Orc clans are in constant conflict and rivalry, over territory, pseudo-political offense, or simply generations-old grudges. These wars can last as short as a few days, or as long as centuries. Orcs are nothing if not stubborn, and for a clan to concede a grudge is rare to the point of being unheard of.
That said, such conflicts as these operate under a strict set of rules set out by Vial and Grate. And no matter the deep seated-ness of a grudge, outside threat is more than outweighed by the loyalty between orcish kind. One of these strictures is that in time of external war or conflict, all orcs must put aside any and all of their internal strife and unite under one leader.
The Gratechosen.

Chosen of the Right Talon

The Gratechosen is not just an orc chieftan of especial power. It is a position of absolute authority over all of true orcish kind. The Gratechosen, purely as a result of being the Gratechosen, is stronger, smarter, and more powerful than any other orc. To defy the Gratechosen is a breaking of pact in the highest degree.
But orcs are slow to accept authority. When the call of a Gratechosen is sent out, orcs answer, but not necessarily to bow down to their new ruler. Orcs come to test the self-proclaimed chosen one. Tests of strength, intelligence, and above all, the ability to command the Witch-eyed. To impersonate being a true Gratechosen is not just a prevarication against the gods, but it is an utter defilement of all of orcish kind. Such imposters are given no succor. They are tortured, driven to madness, and exiled.
Any orc, from the greatest chieftan to the lowliest outcast, can become the Gratechosen, for in the eyes of Grate, all orcs are equal. It is said that to become the Gratechosen, one must have the favor of Grate. In ages gone by, it is said that the chosen one would receive a vision, or even a visitation, directly from Grate or one of his priests. But in more recent years, orcs have had to rely on signs of nature. The way the wild beasts hang about the chosen, the way their eyes strike fear into the heart of any who gaze upon them.
Some are disturbed by this lack of divine intervention. Some say that it is a sign that Grate and Vial have deserted their people, and as a result the existence of a Gratechosen is an impossibility. They are usually discarded as crazed shamans, but some of these orcs have banded together, into a group of self-designed "forward thinkers", whose goal is to bring what they see as a deserted people to a new age of prosperity and dominance.