Herein shall be put information concerning that great power of evil, Erag. In a little bit. I have the information but just need to put it up here.

Areth,
Ka

What does it look like?

Because Kitra so kindly began the conversation on the topic of appearances, I will begin there.

Erag was not always so called, but was Mauril, greatest and most bright of the Attar. He was in the beginning in form as a great and tall man, but void of human parts and organs, having no need of physical subsistence nor procreaation, being sustained rather by the light and life of Eos, he who alone is. For it was given to the Attar to be though a part of creation yet not bound to it by mortality.
But as Mauril led some of the Attar into sin, the light within him became marred by color, no longer pure white. So he shone with red light,
fierce and angry, when he led the Min in their rebellion against Eos.

When the great rebellion failed, Mauril was cursed to be forever manifested in the body of a great serpent.

Here is what you would experience if you came upon Erag at this point after the fall. Sorry for the huge change in style. I forgot I had this old draft. Same information is conveyed though.

So you're walking through a creepy bit of forest, and it's kinda gloomy. So you're a little spooked.
Then it starts getting darker. And it's not that the sun is going behind a cloud, or the trees are getting closer together.
No, it's not that.
There's a mist coming towards you, like the smooth curling tendrils of a candle's smoke right after you blow it out.
But black.
The darkness continues to swirl thicker and thicker around you, and you realize that all sound has been muffled. It's peculiarly frightening - isolating you almost to the confines of your own mind. Cut off from the physical world.
Then the source comes.
First you see the red glow. Coming closer.
Then you can pick out bits and gleams of a body. But nothing for sure.
Finally the red light rises into the canopy of the trees.
When you look up at it, you see everything.

It is a huge serpent, of dragonic proportions. His eyes glow red, but not like an LED light or something like that. No. He has a black slit of an iris, but everything else is the swirling red of flames held at bay. Just beneath the surface of his eyeball is the pent-up passion of Nebuchadnezzar's furnace, as it were.
The light pulses and swirls.
I suppose like the eye of Sauron. But different, of course.

His scales are black, with a matte finish that sparks a reflective gleam here and there. The darkness seeps out of his scales, flowing back and around him like the influence of his mind to control the elements of the world.
Under his scales, and between their joints, the red of his light peaks through, dormant and yet raging. This light, too, pulses with the same pent-up power.
You know that he is physical, and yet does not follow the rules of the physical. He is a being altogether different from any animal or creature of the forest.
He is Other.
He is Power.
+++

Oh, and if you look into his eyes, he can subsequently change your emotions. :\ If, that is, you are not a Follower.

But those things should be explored in a later post.

Areth,

Ka

So much for the physical appearance of Erag.

His spiritual power is by far the more dangerous and powerful of his assets, rather than the pure physical power of his body as a serpent.
Erag's power over humans manifests in different levels of spiritual connection/influence.

The simplest connection is called a brand. This happens to any human with whom Erag makes purposeful eye contact. Subsequent to a branding, Erag can influence (not control) the emotional state of a person by consciously focusing on them. He is also aware of the emotional state of those near the branded individual, as well as the individuals general location. When Erag is not focused on a branded person, they go about their life pretty much just like normal, although there is a decided lack of purpose in what they do - they become rather lethargic, like a reptile on a cold day. However, Erag can issue direct mental commands to a branded person before changing his focus to another person(s), thus giving a direct purpose to that person, which will drive them to act until it is fulfilled.

A deeper form of connection is called a seal. A seal is much like a branding, but to a greater degree. It is formed when someone gives a particular three-fold oath to Erag, which he seals by breaking the physical/spiritual barrier and embedding a splinter of himself, as it were, within the sealed individual. Properly speaking, this is not a metaphysical change of the individual (who remains fully human and unmixed in being as a human), but it is the clearest way to explain the results. Subsequent to the seal being made, Erag can directly control the emotional state of a person, communicate mentally, and even take over some bodily functions (i.e. speaking through a human instrument). A seal is, quite frankly, demon-possession. Erag can sense the emotions of those physical near a branded person, and can if desired see through their eyes (at which times the human would not be able to see). However, Erag rarely does this because he knows the exact location of the individual. [Those who have received a seal from Erag have formed a group, calling themselves the Sulveri, which I think can be translated "servants of the great serpent". They are powerful influences in the world.] There are also changes that happen to the sealed individual. They can themselves sense the location of others, their emotional state, and their physical abilities are heightened: greater endurance, speed, agility, and at times, when particularly focused on by Erag, supernatural power over some aspects of the physical world (telekinesis, pyrokinesis, etc...)
Erag is only able to focus fully on one Sulveri at a time. Also, there is a sense in which the seal acts as a drug. The more it is used, the more the sealed individual wants and needs Erag to focus directly upon them. They go through severe withdrawal phases after particularly intense use of the seal by Erag. Thus each of those sealed are always seeking to impress Erag and keep his focus upon them. When he is not focused on a Sulveri, he must give them a specific, direct task to complete, or they will essentially go crazy trying to gain his attention by wreaking mayhem and ruin around them by whatever means they can devise.

To solve this problem, Erag can "loan out" those whom he has sealed to other Gaurim (fallen Attar, aka devils), at which time the other devil will take direct and complete possession of the person. There is pretty much no going back from this, however, because the human is so broken and incomplete without the demon after a full possession of that kind that they are incapable of being any further use to Erag. He tried. It's like being addicted to huge dosages of a very powerful drug and then trying to go back to something much weaker. Severe withdrawal follows the severing of a full possession, and can only be remedied by the resumption of the possession.
Such individuals are still useful to Erag, however, though the lesser devils tend to be more problematic because they are harder to control as thoroughly. They are much more prone to acting independently of the master plan.
Individuals who have been sealed by Erag and then possessed by a different devil have much greater supernatural powers over the elements than a mere Sulveri does. However, these powers are specific to the devil that inhabits them, and don't change or increase. For example, if the devil grants the human pyrokinetic power and increased speed and agility, those are the only superhuman abilities that the person will have while possessed by that devil. Another devil may be able to grant other powers, however.
Humans who are directly possessed have much shorter lives, and tend to be heedless of their own health, and can ignore the pain of fatal wound - but the physical reality still takes its toll. Most devils, who love possessing bodies, dread the death of their human host because they will be forced back into a formless existence in the spiritual realm - so the tend to make sure that their host remains healthy. However, in the heat of the moment, they oftentimes forget the limits of their hosts, running them into the ground well beyond the limits of human endurance.

(One last kind of demon possession is that which does not involve Erag at all is when a human seeks demonic possession and a devil takes advantage of this. This is very similar to the kind of possession explained above, but there is no seal to Erag, so the original human spirit has no connection and submission to Erag - instead acting purely as the devil that possesses them leads. They do not act within Erag's master plan. They are rogue evil men, often known as necromancers and wizards and the like. They often rise to great power. Their powers are often greater than those who are in the third category, and their lives correspondingly shorter.
A demon can only take possession of someone if that person is seeking it.)

There is one other subject pertaining to Erag, which is his master plan, and how exactly he goes about trying to destroy the work of Eos, but that will be reserved for another day.

Areth,

Ka