Nicholas 'The Silent Sword'.
An assassin that works entirely differently from the other assassins. His giant sword was easily recognizable, as well as the path of destruction that was left during one of his missions. From what Lyle could gather, Nicholas was always like that, even back when he was a lower-ranked assassin, he used his giant sword to kill all his targets.
Get in without being seen, then decimate the target as well as anybody that was present before leaving without a trace.
He didn't care about other people realizing it was him that had killed the target.
The only reason Lyle found out that it was him that had killed Monas and the vamps was that the trio that was in the house never heard a single thing. One blow was enough to kill Monas and his vamps and to completely destroy the array that had been placed in the hideout. The cut on the wall was thin because it wasn't made from his sword but from the remnants of the mana that left the sword.