Ogryns are one of the few types of abhumans tolerated by Humanity. Despite their limited intelligence and crude speech, their devotion to the God-Emperor and the Imperium is unshakeable. Most commonly seen serving in Astra Militarum regiments, these giants are valued for their monstrous strength, remarkable endurance, and uncompromising loyalty. Ogryns always fight in the front ranks and can survive wounds that would prove fatal to ordinary humans. To most, they are nothing more than weapons of war existing to be unleashed against the enemies of Humanity; weapons that may prove equally deadly to their masters should they ever lose control of these soldiers. Despite such risk, Ogryns remain an integral part of the Imperium's forces and are employed daily in thousands of battles taking place in every corner of the galaxy.

Conscript O-118-B is a rarity even among his own kind: a so-called Bone'ead, an Ogryn with a special-issue cortex augmetic that has enhanced his intelligence and granted him the ability to memorise and interpret orders beyond the most basic. This Ogryn once marched in the ranks of the 27th Regiment of the much-renowned Scintillan Fusiliers, stalwart Astra Militarum troops recruited from among the sons and daughters of Scintilla's noble families. While he saved the lives of his fellow Guardsmen more than once, they refused to treat him as one of their own, giving him the mocking nickname “Cogg” for the similarity of his thought process to the workings of a cogitator. Undaunted by their dismissive attitude, Cogg continued to serve the Imperial Guard and Humanity faithfully until tragedy abruptly ended his affiliation with the 27th.

Left to his fate, the Ogryn might have disappeared into the depths of Hive Sibellus forever, had he not met a unique individual, an acolyte of the Inquisition, who decided to lay claim to this discarded instrument of war. Although he may still be confused about this sudden change of circumstances, Cogg follows the orders of his new commander and wreaks havoc on the enemies of Humanity with the same dogged determination. Soon he will learn if he can become something more than a mere tool in the hands of his master, or if he is destined to remain a nameless weapon in the war machine of the Imperium.