Martial Prescience

When target 'Grey Knight' unit that is Set to
Defend is targeted by an attack made by an
enemy model. That Unit gains "Until end of
Phase, Each unmodified save roll of 6 deals 1
mortal wound to the attacking unit"
"Though unnumbered lurking perils await us,
our blades will ever be ready. For we are the
Emperor`s Vengeance!"
-Canticle of Absolution