Who is Ba'alzamon, Shai'tan, the Dark One from The Eye of the World and what is their importance?

Ba'alzamon, Shai'tan, the Dark One is the protagonist of the story, the evil who is behind the Trolloc attacks, directing the Myrddraal, and hunting the three boys. The Dark One was bound to Shayol Ghul by the Hundred, but his counterstroke tainted saidin, the male half of the One Power, and drove the Hundred mad. Those hundred were joined by more and more as male Aes Sedai began going mad from the taint.