Brief Backstory: Long throughout time, the exsistance of 'holy' creatures and 'evil' creatures engaged in a bloody, constant war has been speculated by many. There are many religions that touch on demons and angels, but none so more than the catholic church. The catholic church is in fact, half right when it comes to battling demons. There are many, many kinds of demons and angels out there, and this guide will only touch on the basic principles that all these creatures share regardless of class. Some religions have sought to map out the kinds of demons there are, and even fewer have tried to do the same with angels, but the fact of the matter most all of them are different, much like every individual person is different. These creatures exsist in a plane of reality above our own, and occasionally, due to a weakening in the veil that separates our worlds (The winter or summer solstice, or oct 31st, believed by witches and mages to be the day our worlds are closest connected), or by a curious but naive mage, there creatures are able to leak into this world.
Demons: Strengths and Weaknesses
Demons are an interesting creature indeed, you can have everything from a succubus, a demon that aids to control and feed off of sexual energy to gain power, to that of a drider, a creature similar to a centaur, only ending up as half spider, half human. The strengths of a demon vary based on the body they inhabit, or the anchor that binds them to this world. A typical demon's strength could equate to the power of a sanguine augustine, while the more powerful ones can even rival a master.
Strengths: Demons are very cunning, their aim in this world is to feed off of fear and negative emotions, emotions that cloud your judgement and lead to dispair such as pride, guilt, lies, pain, grief, to only name a few. A variety of demons tend to search out innocence and exploit negative events in their life. Like a parasite, once a demon had managed to burrow it's mind into another, they begin to feed off of the negative energy the individual has. The demon can plant seeds of thought into a person they've managed to attach to, furthuring the negative emotions of attitude someone with a 'demon on his back' would produce. In extreme but rare cases, this can lead to a full possession, in which a demon, lacking life and puriety but desiring it, will attempt to take control of an individuals body in an attempt to steal what it has, this ultimately kills the individual who's been possessed, but has been known to take years to accomplish.
Demons of course aren't limited to only trying to posses an individual to obtain sustance, some demons rely on the greed of humanity, and feed off of the drive that pushes chronic gamblers to risk everything they have. While others might exploit the sexual or curious nature of humanity and drain their target of energy that way.
Weaknesses: There aren't many known weaknesses to a demon, destroying its body is one way to temporarily misplace the soul of a demon, however at this point a demon could just bide his or her time and reobtain another host through corruption of the innocence or already corrupted, one thing that the catholic church has gotten right is the fact that demons are compelled to obey those with faith and conviction. While the church belives that it is the power of god, or his symbols that do this, it is actually the one with that faith whom has the ability to banish a demon, understand that we're talking about true faith and conviction, an average religious joe wouldn't be able to pull this off, especially considering the amount of fear in a person a demon can bring out if they need to, those gifted in the more magical arts are also able to banish a demon back to its world by setting up a complicated ritual (For witchcraft users) or by use of a sealing spell (innate users).
A demon can also be banished if you were to destroy his anchor, every demon has one. An anchor is an object that the individual would keep close, it is in fact the very thing that ties them to the mortal plane, often charged by a mage through a complicated ritual involving the invocation of a demon, if this item is destroyed or damaged it will weaken or destroy the demons hold on the mortal plane, forcing it back through the portal of that which is came through.
Demons have a remarkable resistance against bullets to non-vital areas, however a shot to the head is just as effective as it is with any creature, it will destroy the body and force the soul of the demon to wait for a new host. When a demon enters this plane it can either do so in its actual form or take on the body of a host, however a mage would need to have a sacarifice prepared that the demon could shape into a host, without the sacrifise, a demon being summoned will have to find one on its own, which is not only time consuming, but exhausting as well. A demon without a host body or its own body can only survive in the mortal plane for 3 days. Vampires, Lycans, and those gifted in magic are able to sense the precence of a demon, and seals and wards can be placed on individual rooms or small homes to prevent a demonic inhabitation.