The faizera is, to begin with, an intelligent creature. It's also an observant, curious creature that seems to just watch people. This has led to a number of theories about the birds, most of which are pure speculation. Combined with the power of their quills and the way the birds monitor but avoid people, some believe they are messengers of the gods.
The quills are hard to come by. The birds are extremely fast and look a bit like multi-hued falcons. Hunting them is banned by most cultures, and loose feathers are rare. On occasion, however, there will be a cache of feathers found in an abandoned nest or strewn in a fairly inaccessible gorge. And, once in a great while, a dead faizera...it is believed to bad luck just to see a dead faizera, and far worse to disturb it, but the gleam of easy money will mean the bird disappears almost as soon as it's found. Once in the hands of smugglers, the "cursed feathers" are almost impossible to tell apart from feathers that came from a live bird...though the prices mean that some will use magic to determine the source or to question the brokers.
What, then, makes the feathers so highly sought-after? The feathers, used as quills, will write in any language the writer desires. The language is perfectly clear in the writer's mind so long as the quill is in motion. The quill can be used for a long time...for a quill, anyway. Most will last for about a month, which is considerably longer than a typical quill. Whether it is used heavily or not, after about a month the prismatic color on the feathers will begin to gray, and all magical ability will cease to function.
There is a major caveat, in that the quill will only write in the first language it is used for, and it will only write for the first person to use it. If you have one and begin writing in your native tongue, that's it, you're stuck with an extremely expensive quill that doesn't do anything differently than a cheap, ordinary quill.
Can you read in the chosen language? Yes. The quill will still work only for its owner and the read language will be the one first written in, but as long as the quill is in possession, its owner can freely read in that language as well as write in it, though the writing still requires the quill...the comprehension of the language is magical and will not translate to the written word without the quill.