The opposite of the Serpent Of Chaos, and one of Oberon’s parents.

Corwin sees the Unicorn:

“…a soft, shimmering white encompassed it, as if it were covered with down rather than fur and maning; its tiny, cloven hooves were golden, as was the delicate, whorled horn that rose from its narrow head. It stood atop one of the lesser rocks, nibbling at the lichen that grew there. Its eyes, when it raised them and looked in our direction, were a bright, emerald green. It joined us in immobility for a pair of instants. Then it made a quick, nervous gesture with its front feet, pawing the air and striking the stone, three times. And then it blurred and vanished like a snowflake, silently, perhaps in the wood to our right.

I rose and crossed to the stone. Gerard followed me. There, in the moss, I traced its tiny hoofmarks.”

Gerard and Corwin discussing the Unicorn, pages 79 and 80 of Sign of the Unicorn

“Julian claims he once saw it,” [Gerard] said. “in the distance. Says his hounds refused to give chase.”

“It was beautiful. That long, silky tail, those shiny hooves…”

“Yes. Dad always took it as a good omen.”