[@Guilty Spark] I need to see how it make sense. I mean sure why not? As long as we don't get "I can summon Satan".

[@Leslie Hall] *Scratches head* Let's not make things complicated.

[url=http://fairytail.wikia.com/wiki/Demon]Your brand of demons[/url] 

As long as they carry the same shtick.

[quote=Reference]The appearance and abilities of Demons vary, although there are a number of common traits which many of them share. Such traits may include horns, pointed ears, claws, tails and leathery wings.[1]
There is a subspecies of Demon, known as the Etherious, which is comprised of Demons born from the Books of Zeref.[2]

Demons and it's sub category Etherious carry Demon particles within them then by all means all demons do carry it too. Not all demons can use curses, they can also use magic.[/quote]