Transhuman Physiology

Use this Stratagem when a GREY KNIGHTS
unit from your army that is not a VEHICLE or a
SERVITOR is chosen as a target for an attack.
Until the end of the phase, when resolving an
attack made against that unit, an unmodified
wound roll of 1-3 always fails, irrespective
of any abilities that the weapon or the model
making that attack may have.
Space Marines have reserves of willpower that allow
them to fight through even the most grievous of wounds.