Legends, stories scattered through time. The Grimm have kept their true tale alive, passing it down so none forget.
Back before the time of man and Grimm, the world was dying. Drowning in fear that all living things emit. Seeing this, the spirits (twins of light and darkness) knew that something must be done so their creation wouldn't parish. Taking some of the earths fear, the twin of darkness created the Grimm. They absorbed the fear thus saving the spirits creations. But balance was not reached, for now the creations of darkness outweighed those of light. Needing balance the twin of light took the now purified dust of the world and made man. The spirits thought peace and balance was made, but what happened after was nothing short of horrific.
Man gave off fear, like all living things to do, but this fear was different. It was stronger, felt sweeter, and was extremely addictive. The Grimm became more aggressive in the need for this fear, slowly going mad because of it. Then tragedy struck when the first man was killed. The fear that followed the death was the last nail in the Grimm's coffin. For a Grimm that kills a man will become lost forever in the grips of insanity.
Those that were still sane hid. Staying as far away as possible. Sometimes they encountered man, these occasions usually ending badly for one or both parties. Though the number of these Grimm are dwindling, they endure. Hoping the spirits vision of peace and balance can become reality.