Perched upon stone, it stakes its claim, Angelic wings, but satanic in fame.
Thou shalt know why, so thou shalt see it not.
Now let the fates bring the plague!
Addition: The answer is supposed to be a mythical creature.
The answer to your riddle is a gargoyle! Gargoyles are mythical creatures that were stone* statues that were perched* upon castle walls in the midevil times. They were thought to protect the castle, and at night, when no one was about, they would come to life and fly into the streets and wreak havoc amongst the kingdom.
a crow?
*is confuzzled*
they're dark in colour but have feathered wings like an angel. and they spread diseases.
They're around more at night so i guess you wouldn't see it during the day.