The Sorcerer Commands The Aspiring Sorcerer who leads the squad is a psyker. If the Aspiring Sorcerer is killed, the Thousand Sons marines roll a single dice for their Slow and Purposeful movement, unless the squad includes an Independent Character with the Mark of Tzeentch from the beginning of the turn.
Fearless Fearless troops never have to fall back and are assumed to automatically pass any morale test they are required to take. They can never be pinned. This special rule is gained by any independent character joining a Fearless unit. Also, as long as a Fearless character stays inside a non-Fearless unit, he loses this special rule.
Slow and Purposeful Models with this ability always move as if they were moving through difficult terrain (typically rolling two dice and choosing the best as their movement rate). In addition to this, they are always treated as stationary when shooting, and never receive a bonus attack when charging into close combat.
