Naraku (奈落, Naraku) is the series' primary antagonist. Naraku is responsible for many of the characters suffering, including the death of Kikyo and the sealing of InuYasha to the scared tree. Naraku originated from a bandit named Onigumo, who made a deal with several demons in order to receive a new body so he may pursue his caretaker, Kikyo and gain possession of the Shikon Jewel. Throughout the series' run, Naraku has created many detachments, to aid him in goal of killing those who oppose him and finding the shards of the Shikon Jewel. In the Japanese anime, his seiyū is Toshiyuki Morikawa and is voiced by Paul Dobson in the English adaptation.

Source: Wikipedia