Phases of a lunar eclipse
The Nyrolian Owls are owls that are hatched during a lunar eclipse. An enchantment is put on the owlets that grants them great power. Whether it leads to great evil or great goodness of spirit depends on the individual. It was also a night when magen was strong and Nyra believed that she could use the lunar eclipse to hatch a new generation of hagsfiends.
Nyrolian owls usually have a name that begins with "Nyr", such as Nyra or Nyroc, which are the names traditional to such owls. The name 'Nyra', at least, seems to originate from a female Barn Owl from ancient times from whom legends of the Nyrolian Owls apparently started (though unconfirmed, the Nyra of legends might have been the first Nyrolian Owl, or at least the first to be chronicled). These owls include the first king Hoole, Nyra, and Coryn, formerly known as Nyroc, the second and third who bestowed their birth names per tradition. 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, is that they develop a large glowing white face that resembles a full moon. It is not known if other species of owl experience such physical changes.