Dul'akor

"'In the beginning, there was only the light and the darkness; and from the darkness came the greatest terror of the cosmos, Dul'akor; the Abyssal One.'"Dul'akor (Dul-akor), also known as the Abyssal is the strongest of the Defilers. He was forged out of pure chaotic energies that polluted the stars after Eozur was banished, and such radiates with impurity and malevolence. A being that held a singular purpose to destroy and consume light, lead him into direct conflict with the Celestials.

Dul'akor was regarded as a mere hound in the eyes of the Celestials, but appearances can be very deceiving. His singular thought was towards consuming the Celestials.