Heilo the Blind was an old Spotted Owl (Strix occidentalis) who was, for a while, a weather interpretation ryb for the The Great Ga'Hoole Tree. He retired around the beginning of the Age of Enlightenment and was soon blind.
As time had passed since the arrival of the rainbow caterpillars to the island, Heilo began to get odd twinges in his gizzard. Unable to see the luminaspheres, Heilo was immune to their bewitching effects. He couldn't put his talon on it, but he knew something was very wrong. He shut himself in his hollow for a period of intense and undisturbed meditation, and finally sensed the true nature of the tree's recent sickness. At once he knew the cause. Despite Sianna's protests, he informed the Parliament, which ordered the destruction of all luminaspheres and the death of all the rainbow caterpillars on the Isle of Hoole. And so it was done.
Later that year, Heilo the Blind was hailed as a hero.