The Wyld Hunt in-game

In character, the Wyld Hunt was founded by Shemkel Mornheneb, a scout hailing from Rivendell, during his grief and sorrow-filled walkabout through Eriador.
One day, when he trusts you and you manage to convince him to open up, he might tell you the reason of the walkabout. For now, it's obvious that he lost someone. Judging by his pendant, someone very close to him.

During his travels and guerrilla-like hunts after various roaming orc bands, he found himself in Enedwaith, stranded in the unfriendly land of the Algraig. There, after dozens of years wasted on self-loathing and blind hatred towards the orcs, Shemkel met the Huntsman, a mysterious Maia of Oromë.
What was said and done during that period, shall forever remain Shemkel's secret, but the meeting changed him greatly. Or, perhaps, restored to sanity.

According to his daughter, Aralynia, when she met him after all those years of abandonment, the change went in deep. The hatred was still there, as well as the grim determination to hunt and slaughter every orc he comes across.
But there was something more. Regret, for the fall he brought onto himself. Conviction to atone himself in Aralynia's eyes. Finally, the sense of purpose.
No longer was Shemkel torn between the desire to leave the Middle-Earth or plunge himself blindly into purposeless killing.

Guided by the Huntsman, Shemkel began to seek other, like-minded free peoples, in order to form the Wyld Hunt that elves of Rivendell know today.
Though never numerous and decentralized, the Wyld Hunt proved to be a useful and reliable organization, dedicated to defending free peoples against the servants of the Enemy.
No longer single-minded focused on hunting the orcs, scouts of the Hunt, following Shemkel's example, spread throughout Eriador to seek out hidden dangers, cooperating closely with Rangers of the North.
Yet, while Rangers devoted themselves to settling in the lands they chose to protect, the Wyld Hunt always roamed, always hungry for new enemies, new skirmishes, spread and vigilant, meeting in great numbers only to hunt and kill a formidable enemy or cull a big and dangerous warband.

From Ered Luin, through Shire, Bree-land, to Trollshaws and even Angmar, the Hunt never stops, though free peoples, bar a few well-informed leaders, remain oblivious to this struggle. And even though their numbers were always scarce, Shemkel knows well, that the vanguard and scouts are crucial in every conflict. Hence, he tries to eliminate as many scouts of the Enemy, as possible.

Having surrounded himself with other, like-minded people, Shemkel drives the Hunt to help the Free Peoples in their struggle against the Shadow growing in Angmar.