Spook Anima briefly become Untargetable every 8s. The next attack after leaving the Untargetable state is guaranteed to Critically Hit, and the Crit DMG of that attack is increased.
Spook was added with the synergy: "Spook Anima briefly become Untargetable every 8s. The next attack after leaving the Untargetable state is guaranteed to Critically Hit, and the Crit DMG of that attack is increased. 2/3 Anima give 70/150% ."