Vassa Kynro is...

... Well, nobody knows what it really is. There are theories, though: a demon under the banner of Vassago who was called from Hell due to a failed summoning, an elemental born of the emotion of the dead within the halls it was conjured, or simply a thing created from misused magic and mortal will. What is known is that it's a cold creature that has an instinct to protect. Only in recent years has it begun to show a faint hint of personality, likely adopted from the few masters it has had since its calling to the mortal plane.

What slivers are known of its past come from documents found by its current master, Rasasha, and its own incomplete memory. It was called by a monk in France after the construction of the Parisian catacombs in 1792, in order to protect the place from grave robbers. It was left there, forgotten; in time, its master died, but unaware of the fact, Vassa never tried to venture outside.

During WWII, when a portion of the catacombs was converted into Bunker Allemand, it came across a German soldier: Luthias "Coder" Herzog, a man who really didn't like the way things were heading and wanted to bail out. Although Vassa initially considered him a threat, Coder managed to stop Vassa and--after a week of work--coax it to his side to help him return to Dresden to get his wife and daughter and protect them as they fled Europe altogether.

As a result, its first exposure to the outside world was to a warzone. Unfamiliar with the weapons of man, Vassa failed to protect Coder, though--still bound by orders--it continued its trek to Dresden, secured his wife and daughter, and followed them to the United States. Because it was also bound to these orders until dismissed, it remained a guardian until the now-elderly child told Vassa it could leave. Confused as to what it should do, it wandered aimlessly until the will of its current master beckoned it.

It now serves as an, uh, unorthodox method of exorcising evil spirits. Fight fire with fire, as they say.