The Nyrolian Owls were a selected groups of owls that were hatched during a lunar eclipse. An enchantment was put on the owlets that either led to great evil or great goodness of spirit and power.
Many Nyrolian owls had a name that began with Nyr, such as Nyra or Nyroc . Owls that bore this enchantment include the first king Hoole, Nyra, and Coryn, formerly known as Nyroc. Hoole and Nyroc displayed the good side of the enchantment; while Nyra was the evil side.
One of the physical effects of the enchantment, on barn owls in particular, was that they developed a large glowing white face that resembled a full moon. It is not known if other species of owl experienced such physical changes.