The werewolves once were very strong. They had hundreds of packs roving through Europe. They were one of many shape-shifting peoples of the earth. Just like the wolves, there were half human half animals of all kinds. Almost anything that was a natural predator had some sort of half human counterpart. From tigers, to leopards, to bears, to snakes, to foxes, to hyenas, to lions, to jackals, to crocodiles, all had were-counterparts. Lycanthropy, the disease that carried the wolf trait, mixed with human DNA all too easily, and spread quickly. Human rulers saw this as an epidemic. Feudal Europe was preyed upon without any distinction between nobility, clergy, and commoners. Whole towns were wiped out by packs of these wolves during the full moon. The wolves were immune to most diseases and did not age, unless they willed it. Such was the power of regeneration that was given to the creatures. A were-creature of any kind could appear whatever age they willed to, and return to a previous age if desired. That was what made the wolves so dangerous. During the other phases of the moon, they would appear whatever age they wanted, infiltrate towns and be trusted by the people, only to destroy those people come the three nights of the full moon. On two of these nights, the first and the last, the wolves would maintain their full human minds. They could control themselves to the extent of cutting themselves off from humans, but if one got close, they could not fight the bloodlust. But second night of the three, when the moon is at it's fullest, they cannot control the urge. They ravaged, killed, and fed. Their victims either died or were turned into more of the infected creatures.
Then came the time of the Black Plague. This was one disease the werewolves were not immune to. Their numbers decreased significantly, as did the humans of this time. Those humans who survived knew that the same problem would return, if they did not find out what could kill the wolves. Unfortunately, any person that went out to fight them never returned to tell of weaknesses found. Until one day, a silversmith whose family had been slaughtered by the wolves hunted them down and killed them with one of his handmade blades. He returned with the secret to killing the already depleted wolfen packs. He created a group that called themselves the Were-Hunters. Using their silver weapons, they hunted the wolves to the brink of extinction. Some of these Were-Hunters moved on to other parts of the world to combat the other creatures that plagued mankind. Some of the Weres learned to control it, to shape shift when they wanted and only then. This made them harder to recognize, but it still wasn't enough. Even with the powers under control, the Were-Hunters made no distinction as long as they weren't fully human or fully animal. Only a few of the Weres survived this time, and those that did went into hiding, and all that survived were the ones that could change at will.
Eventually the Hunters, for the most part, decided they had killed off the creatures. Many disbanded. But a few groups stayed together, continuously hunting the Weres through the night. Eventually this battle came to the New World as well. The Were-Hunters raised their children to hunt, and Weres of all kinds raised their children to stay hidden from the Hunters. The ability to change at will was passed down through the generations, as once a Were learned it, all its descendents, whether born or bitten, would inherit the ability to as well.