Prototype Legionaries were functional prototypes of Space Marine Legionaries, who were created before the process was perfected by the Imperium.
Known as the Primordial Strain, almost none of these initial prototypes are known to not have survived the process of becoming Space Marines but they nonetheless formed the basis of the initial culture of the First Legion. The process first began around 550.M30.
They were unrefined and ill-favored, when compared to Legionaries, but were still potent and served as the bridge between the unique power of the Primarchs and their sons. The vast majority of the Prototypes were born of the Primarch Lion El'Jonson's Gene-seed, as it was noted for its stability. At least one, however, was created from the genetic material of the Emperor and the Perpetual Erda.
- Abraxus Ghent - Created from the Primarch Lion El'Jonson's Gene-seed.
- Leetu - Created from the genetic material of the Emperor and the Perpetual Erda
- 1: The Horus Heresy Book Nine - Crusade, pg. 83
- 2: Saturnine (Novel), Part 2 - Chapter 3
- 3: Horusheresy.com Galaxy Timeline (last accessed 2/6/2022)