Thread:Algrim Whitefang/@comment-37909923-20190130035046/@comment-3055683-20190130042158

To answer your question they are a part of an Alternate Universe (AU) project called the Legiones Astartes. Here's the gist:

"The Praetorian of Terra, Rogal Dorn, proposed that the Imperium should not only seek to rebuild the Legiones Astartes numbers, but to eventually expand them even further, by creating new Legions. To help guide these future Legions, they would fall back on the wise tenets of the Principia Belicosa, with additional wisdom added to it by Dorn himself. With the death of the strategically brilliant strategist and organiser Roboute Guilliman at the hands of Alpha Legion assassins, Guilliman's proposed treatise, the Codex Astartes was never completed, and therefore, never adopted. Thus, the dissolution of the Space Marine Legions into separate Chapters never occurred. Soon, the old Legions were rebuilt and returned to the field of battle, joined by brothers of a new generation, seeking to prove themselves in a new war against the Emperor's enemies.

The Soul Drinkers are merely one Space Marine Legion in this AU...you can check out the rest of the project here:


 * Warhammer 40,000: Legiones Astartes Community Project