The Grimm Monsters are completely paralyzed by the runic seals Ive added to their heart and Inheritance Core.
Hun!
The seals are not perfect, which is why I was going tear the heart and their Inheritance Core apart when I sensed something from my link with Nero; I was about to examine the rough jumble that Nero had sent me when I noticed a sneaky Grimm Monsters coming toward me.
This Grimm monster was hiding quite a distance away from the fight, and the moment it had throught, I had let my guard down; it had attacked.
It would have been a perfect kill if my soul sense had not been working here; I would have at least grievously injured by its attack if not dead seeing the speed it is coming toward me.
Unfortunately for it, Ive discovered it, and I still have a few seconds remaining before the power of the 'First Blast' wore off, so it had to die.