[Dagonlives]

A paladin of Amaunator wanders into the library of the Moonglow Keep, as well as the other sources he may have access to, inquiring upon how to invoke and banish beings of shadow.  He also asks for relevant background to the planar beings, so that he may educate others who will be necessary for future work.

[sharkinajar]

The paladin does find some information on a few different types of shadows. The shadows that bleed out from the Plane of Shadow, a strong intent that remains behind when the owner dies and the soul passes, and those conjured by mages using a link to the Plane of Shadow. The shadows are usually unintelligent and mindless, only filled with the longing left behind. Those naturally from the Plane of Shadow show more intelligence, but they are quite rare and do not have the longing the others hold. Banishment of shadow is almost always simply destroying the shadow, but sometimes it can be bound to an object and will vanish when the object is destroyed.

There is little to no information on the actual beings from planes... at least with that vague of a request, the librarians could not help you.