Sleepwalker

The Sleepwalkers were dream police. In that capacity, they apprehended any beings that invaded the sleeping minds of humans. Sleepwalker was tricked by his long-time foe, known as Cobweb (who, like Sleepwalker, had a real name that is unpronounceable by human language), into entering the mind of one individual (a New York college student named Rick Sheridan) and became trapped.

After a few confrontations in Rick's dreams, Rick reacted by tearing off Sleepwalker's Imaginator (a badge-like device worn by sleepwalkers used to teleport around their home plane, the Mindscape). This resulted in an unusual situation, further linking the two. When Rick slept, Sleepwalker could materialize in reality, or he could stay in Rick's mind and converse with him via his dreams. It was through a conversation in dreams that Sleepwalker was able to dispel Rick's initial fears that he was a malicious entity and work out agreeable terms to cohabitation.