Friend? Foe? Wizard's shape? Pet of wisdom? Child stealer? Child protecter?
The Goblin King's traveling form of a mostly white barn owl is such a double sword that you can not really tell
who's side he is a symbol of without taking a side yourself. But then, I think he likes it better that way...

The color white:purity, innocence, secrecy,

( Side Note: In the meaning of flowers, a white rose is the symobol of a loyal, peneting love.
a love able to capivate secrect thought, and a token of early marriage.)

The owl's symbol itself across the world and time:
Aniqute Greece:Foresight, also sacred to both Athena (godness of wisdom), and Demeter (godness of the harvest, fertility, and wheat).
Honored for wisdom but feared, for it's call or sudden appearance could fortell death.

The Middle East: Evil spririts were said to take the shape of owls to steal children away.

Siberia: Owls were kept as protectors of children.

Africa: Sorcerers in the shape of owls caused mischief in the night.

Japan: An unlucky smybol all but the Eagle Owl, revered as a mediator between humans and the gods.

North America Indains
Pueblo:Though them baleful
Navajo:The restless and dangerous ghosts of the dead
Pawnee and Menominee:Saw them as protective spirits, using their feathers in healing ceremonies.

Celtic:Sacrred but an ill omen, foretelling death, illness, or the loss of a woman's honor.