The Arrival of the Orcs in Azeroth: An Ancient Affair
According to the world of Warcraft lore, the orcs came to Azeroth through a mystical portal, an ancient convergence of magic that connected Draenor, the realm of the Horde, with Azeroth. This gateway to the unknown held the key to unifying disparate worlds, as powerful beings aimed to expand their influence by bridging the gap between the land of orcs and the unsuspecting residents of Azeroth.
Where did the orcs really come from?
The origin story of the orc hordes began during the primordial age of the Dark Portal saga. As far back as that, four old gods (Y’Shaarj, C’Thun, N’Zoth, and Yogg-Saron), the essence of the void’s power and ambition, created the Orcish race in the absence of the Twisting Nether using the corrupted dark magic gathered from the shattered earth. This aberrant magic shaped the orcs, imbuing their essence, shaping their destiny. Here, the key point lies on the fact: The Origin of Orcish Magic was birthed with the Old Gods creating the 1st generation.
After the war ended, this ancient blood feuds from the Twisting Nether, would lead the old-gods-influenced magic infused in early Orcish generation, to cause the Winds of chaos.

| Events | Age | Old Gods |
|---|---|---|
Convergence of the Unseen Energies:
Later, as a pivotal moment was reached when forces of Darkness and Light had ceased their ceaseless strife through the Golden Age, events unfolded by the convergence of unalike celestial energies that caused the birth of a mystical power. Orcs in contact with various celestial powers – The gods of the old Azerothic pantheon & the pantheon of Light, and powers of Darkness -, the most significant powers behind the creation – Crimson Plateau of Unending Sand and the powers under the Sunwell (Wellsprings) were those of primary importance for later events unfolding.
As to the essence of the orc birth, the crucial moment layed in The Wingsong of Darkness and Sun-blessings of the Titans
The origin of the first- generation Orc:
From one of my previous research,
Birth of 4th generation as the primary one Orcs "The Age of the Ancients" ended, which included the Influence of Titans for the Titans’ plan creation.