Morgoth, the Elder King

"I am the Elder King: Melkor, first and mightiest of all the Valar, who was before the world and made it. The shadow of my purpose lies upon Arda, and all that is in it bends slowly and surely to my will. But upon all whom you love my thought shall weigh as a cloud of Doom, and it shall bring them down into darkness and despair. Wherever they go, evil shall arise. Whenever they speak, their words shall bring ill counsel. Whatsoever they do shall turn against them. They shall die without hope, cursing both life and death"
Belegur, the Corrupter does not fully appear in bodily form, neither does he dwell in the realm of wraiths, isntead he occupies both worlds, his powers too great to be contained in either. He seeps through realities like water seeping through a cloth. Nowhere are you safe from his wrath, never are too far from his grasp.