The Effrit Stealth Squad was a specialised infiltration unit within the ranks of the Alpha Legion that operated during the Great Crusade and Horus Heresy eras during the late 30th and early 31st Millennia. This elite force was formed from those Legionaries that specialised in infiltration, stealth, sabotage and assassination.
These operatives were chosen for their adaptive thinking as well as their ability to improvise. The Effrit Stealth Squad was akin to the Legion Seeker Squads found within some of the Space Marine Legions, whose principal task on the battlefield was to identify an enemy's command structure, and slay these officers with a well-placed bolt round while the chaos of battle raged around them.
The Alpha Legion are said to have been the first of the Legions to have developed this tactic and squad configuration, although its use sat poorly within the more honourable combat doctrine of some of the Legions like the Space Wolves. The Effrit Stealth Squad was personally led by Omegon, one of the twin-Primarchs of the Alpha Legion. Little else is known of this elite formation, as the Alpha Legion was notorious for the obfuscation and secrecy that surrounded the internal workings of their mysterious Legion.