Like the later [[Legiones Astartes]], the Thunder Warriors were organized into twenty Legions, each led by a [[Primarch]]. However, unlike the Astartes Primarch'sPrimarchs, Thunder Warriors Primarchs were not physically different from the warriors they led. Instead, they were simply superlative warriors who were promoted to the position by the Emperor.{{Fn|10a}}

The Legions of Thunder Warriors seem to match that of the Astartes. For instance, the 4th Legion of Thunder Warriors was known as the ''Iron Lords'' and specialized in Siegecraftsiegecraft. This closely resembles the subsequent [[Iron Warriors]].{{Fn|10a}}