Abyss was a demonic extra-dimensional being from Marvel UK and an enemy of Death's Head - although Marvel UK no longer runs it is possible that he could return at any point since he is by default part of the mainstream Marvel universe.
Abyss' origins are unrevealed. He has been described as a para-demon. He apparently travels from dimension to dimension, consuming everything in those realms, and then moves on.
Abyss has some undefined past history and enmity with the unnamed father of Argon.
Having consumed everything within one reality, Abyss hungered for the Earth-616 dimension.
Abyss revealed that Death Metal had been an instrument of his. However, since Death Metal had assimilated Argon, and thus developed a conscience, he considered him tainted and lacking in purpose. Abysss created the Soul Slug, intending for it to tear out the essence of Argon from Death Metal. It disgusted him to shatter the emptiness of the Void with matter by doing so.
In order to save the people of a mining colony, Death Metal opened a dimensional warp into which he tossed the bomb that would have destroyed them. Death Metal had no idea where the portal he had created led, but it went to Abyss' Realm of Nothingness.
Whether it was the explosion itself, or simply the sudden entrance of matter to his realm is unclear, but Abyss appeared to be, at least temporarily dispersed.
Argon's father was pleased that Abyss had been reminded that he will do all in his power to frustrate his plans.