Here we have another reskin of the Asylum Demon, but I can appreciate this guy more than the Demon Firesage. This is actually the first boss you can see in the game. You can't fight him early on but he's there wandering around in the Asylum. You're able to return to the Asylum later on to find new items and such. Even a harder version of the Asylum Demon. The Stray Demon has different moves from the regular Asylum Demon to make him stand out over the original. His moveset is pretty much the same as the Demon Firesage, using both physical attacks and magic attacks. He can be quite annoying because of his long range with his catalyst and the explosions he creates cover a lot of ground and deal a ton of damage. However, there's one major flaw to this Demon. You can get him stuck in a loop making him do his butt slam or his close-ranged explosion attack. So it's easy to get a bunch of hits in during this time and rolling away safely every time. At least give credit to the Firesage, he at least will jump away from you if you get to close. As for lore, he really doesn't have any. All you really know is that he's just another boss you can fight when you're able to return back to the Asylum. The OST is the same one used with the Iron Golem. I think it fits both bosses well enough. I prefer it on the Golem because it just looks more intimidating than the jiggly butt demon with a stick. 

Stray Demon boss
Stray Demon OST