Doom Steve

Due to the way they both think, and the strength they both hold, they were as good, if not better of a match then reverse and dark.

Since Orion was killed, and dark was conflicted (took over by shadow, who was sent by void to prevent nightmares plan to become the hero from succeeding) nightmare had no one to turn to but reverse. Over the weeks, he had earned nightmares respect with his cunning strategy and power, but he did scare him from time to time, like his psychotic episode while fighting rainbow for the first time.

And nightmare was a key component in many of reverses plans, who reverse also respected. It was like looking into a mirror. Lights creation was a serious threat to reverse, however, and shadow, a direct supporter of void, resented spark due to his connections with colle. Dark himself was already planning to overthrow nightmare, shadows corruption of him did not affect his hatred for nightmare at all. The indirect pair could easily destroy them both separately. So they fused as a prevention measure, and to wreak some havoc at the kingdoms.



Credit goes to Coldemort119, since doom is his creation.