Darktail

Darktail is a villain in Erin Hunter's Warriors series. He is a large, muscular, glossy white tom cat with blue eyes and a long black tail, hence his name. He is the main antagonist of the first four books of the story arc "A Vision of Shadows".

History
Darktail was born as the result of a forbidden relationship between Onewhisker, a young WindClan warrior, and Smoke, a pampered kittypet. While still heavily pregant, Smoke wanted to join WindClan so that her kittens could be brought up as warriors (Onewhisker having never told her the harsher aspects of the Warrior life). Onewhisker refused, partly because it wasn't the life  for her and partly because he knew he would be in trouble for mating with a non-Clan cat. After much argument, Smoke left, but while on her way home she went into larbour. The only one of her litter to survive was Darktail, and Onewhisker refused to let his kit join WindClan for the same reason. Enraged at this rejection, Smoke declared to Onewhisker that she would raise Darktail to hate his father, the Clans and their way of life.

What happened to Darktail afterwards is unknown, as a very large amount of time (several years) passed between his father's rejection and when he reappeared next. However, apparently his father's rejection and his mother's teachings had a dramatically negative impact on his personality; he grew into a bitterly resentful and sadistically brutal cat. By the time Darktail resurfaced, he had become the leader of a large group of rogue cats that attempted to copy the Clans' way of life. He sought to hunt down the Warrior Clans and destroy them. He and his group joined SkyClan, the long-lost fifth Clan, but later betrayed them and drove them away.

Not long afterwards, a small group of Warrior cats came searching for SkyClan, but came across Darktail and his group instead. They were taken prisoner, but quickly escaped. Darktail and his group followed them to the Clans' territories.

Darktail was determined to destroy the Clans, especially his father's, for rejecting him all those years ago. He and his group eventually managed to take over ShadowClan's territory, pressganging many of its cats into their group. Darktail dubbed his group 'The Kin", where cats followed no rules except their own. At one point, Onewhisker, now Onestar and leader of WindClan, as well as the other Clans, launched a full-scale attack on Darktail and his minions. During the battle, Onestar personally fought Darktail and came very close to killing him, but before he could do so, Darktail whispered in his ear that "that surely a cat who had rejected and killed his own kit would end up in the Dark Forest". Frightened by this, Onestar ordered his Clan to retreat, which cost the other Clans the battle and led to the deaths of many cats and many others being severely wounded.

Eventually, however, SkyClan reappeared and all five Clans took on Darktaikl's group. Most of Darktail's rogues fled and a now fully determined Onestar took on his son, taunting him that he should have stayed a kittypet. Onestar eventually drove Darktail into a lake, where their battle took them further and further out until both of them went under and neither surfaced.