A demon cannot manifest as any thing more than a spirit but can manifest in the physical world as a spirit and that's what's happening when you summon it but that's a complicated and misleading explanation. They are spirits and that sums it up.
They can appear before you in any form they want and many will come to you as animals or humans and sometimes abstract forms. They can also influence the minds of people and animals and in extreme cases that causes a possession.
And so demons can only be seen with the third eye but some people use it without knowing. And they can act like familiars and some demons even are considered familiars.
To Outcast,
I have translated some of Koeting's incantations that he says are an ancient form of Aramaic.
The one that you mentioned that started with "Alash" I have run through Hebrew and Aramaic and have translated it as such:
"Corrupt good God's fire with the dew that is swept away"
The meaning of the incantation I am still contemplating but if any of you are rather weary of being blasphemous (In a Christian point of view) or against a certain religion I would not recommend E.A. Koeting's invocations.
I am translating the other remaining of his recommended incantations and will be posting them on here if any of you are interested.
All the best...
Alas I am not able to post any of the translations yet because I am on holiday and cannot access my works and translations . I will however be writing a separate post on the forums when I arrive back home. Keep an eye out for those interested or curious.
Incantations are used to put you into a state of mind that puts your attention on your goal, in a single minded way that effects your spirit. When your spirit is effected it will start to interact with the spirit realm, wherein demons/spirits may feel what you are wanting.
Due to this any little diddy will do it. Just make sure you really like and connect with what you are saying.
Vibrating the name of a spirit as a mantra is all that is truly needed to call upon them. Drawing out each sound as you say it slowly, building slowly in volume and speed until you sense their presence or they make themselves known. Their name is their calling card. It is generally a title/description not their actual name. But it's important that you know spirit work well, and it's best to do this only after you have been properly introduced through formal evocation at least once.
This is why names are so important. This is why most spirits do not offer their real name until you have gained deep trust between you both. Then they will give you a personal name that connects directly to them. Most spirits I work with also enjoy the use of symbols as bridges. But do be careful about using sigils and seals. You can use them in conjunction with vibrating the name as a more precise focus.
A spirit that is kind to one person may be hostile to another and vice versa. We all resonate with different personalities and natures. This is why formal evocation is recommended, especially at first. There is no true way of knowing how well you will get along with a spirit and whether it will be willing to work with you until you meet with them. Obviously if they're hostile toward you, you want to have that formal ritual and all it's safety precautions and protections in order to keep you safe from harm.