Authors Note: More demons people and I'll say it ahead of time, one will be based on the design of a great writer, and if you're reading this, I hope you don't mind too much.
Disclaimer: Alvin and the Chipmunks belong to Ross B. and Fox Studios, and the story "Demon Hunters" belongs to MetalMunk15.
Hellfire Designs: Demons x4.
Remnants: The true embodiment of negativity, these shadowy spirits are responsible for the most famous cases of demon possession in history. In appearance, they look like shadows with glowing white eyes, and a face similar to a skull, and a pair off arms like a skeletal creature, used for gripping onto their hosts. Unlike the stereotypical spirit, these evil creatures possess their host by means of literally crawling down their throats, latching themselves onto the soul of their host. The effect of a Remnant possession on the host varies, but it usually entails the host keeping their personality intact (for the most part), with the few traits that the host would often keep hidden from society. Other traits include the host's powers and abilities being amplified to their highest level possible (of course keeping a bit of restraint so as not to harm the host's body), and when they reveal themselves to the world in their host bodies, black veins will spread across the body, the lips become black, and often the inside of the mouth (mainly the gums and tongue) will also change to a grey color. These spirits have an odd quirk to their possessions, in the form of an actual time limit for the host to get the spirit out, normally a maximum of four days, after which the Remnant will permanently bond with their host's soul (they can still be removed at this time, but it takes a lot more energy and is more dangerous to the host's soul). Not common, but also not unheard of, a person possessed by a Remnant will have the willpower to overcome the influence of the dark and cold creature currently residing within them, and in rare cases the Remnant will actually be "rehabilitated" becoming more of a secondary personality to the host. The removal of a Remnant from a host's body is usually in the form of using a spirit receptacle in correlation with special magical runes.
Shadow Wraiths: related to the Remnants, these spectral creatures are actually kind hearted beings, often looking like a solid slightly humanoid shaped mass of smoke. Like a Remnant, they will possess people, though only for a second to form a bond with them, one which leaves the shadowy creature completely subservient to the temporary host. After this bond, the Shadow Wraith will either let its master choose its name, or will have already given itself a name, then they can be called upon as a secondary power or strength, allowing the host to perform such acts as shadow keeper, necromancy (death magic), and in some cases even use a vampiric technique called "shadow walking" which consists of literally stepping into a natural shadow, and out of another shadow somewhere the host desires.
Here you go, and I know that it's short, but only because of the length of the Remnant description. Oh, and if any of you are familiar with the Skulduggery Pleasant series of books, then you'll know that the Remnants I designed are based on the creatures of the same name from that series created by Derek Landy, and by that right the template belongs to him.