In just a few short lines, the speaker describes walking out into the heat feeling "ugly as a faction," a strange comparison that suggests something divided, bitter, and at odds with itself. It reads like a person who is out of sorts and doesn't much like who they are. Then the devil notices them, and what he does is surprising. He doesn't tempt or punish. He gives the speaker "myself."
That last gesture can be read in a couple of ways. It might be a gift: the speaker finally sees or reclaims who they really are. It might also be a sting, since being handed your own self, flaws and all, isn't necessarily comforting. The poem leaves that open, which is part of its pull.
The mood is dry, uneasy, and a little wry. The heat suggests discomfort or exposure, and the title's "friend of the devil" adds a shrug of dark humor. The very short lines make the ending land with a quiet thud.