Sixteen-year-old Sybel lives alone on a mountain, with only the mythical creatures that her deceased father Ogam summoned for company.

Sybel refuses to return him, believing that Coren and his brothers would use Tamlorn in their plot against Drede, the king of Eld.

As a result Sybel falls into a depression and resumes her quest to summon the Liralen, a legendary white bird.

Instead, she not only finds the Blammor, a creature of shadow that induces fear, but the wizard Mithran who has been paid by Drede to destroy Sybel's will and hand her over to him.

Sybel – Sixteen at the beginning of the story, she raises Tamlorn with the help of Maelga, the witch.

Described by McKillip as having long "ivory" hair and her father's black eyes, and very pale skin.

Myk – Ogam's father and the one who started the practice of summoning the mythical beasts of Eld.

He is described as having red hair, which is characteristic of his family, and possesses an uncanny and intuitive knowledge of Sybel's legendary beasts.

She is described as being "a thin old woman" with untidy, curly white hair and iron grey eyes.

It proves eventually to be the other, darker aspect of the Liralen, the great bird Sybel is trying to capture.

Cyrin later tells Sybel the same thing, for a similar reason, but, in her case, it has no apparent immediate effect.

A Lyon (lion) who "lived in the courts of great lords, dispensing wisdom, fed on rich meats, wearing their collars and chains of iron and gold only as long as he chose...".

Moriah – Described as being a huge black cat who has a wide knowledge of spells and charms, green eyes, a "sweet silken voice", and "teeth like honed polished stones".

Publishers Weekly wrote "this magical moonlight fantasy has dignity and romance, heartstopping suspense, adventure, richness of concept and language."

Lester del Rey praised the novel as "a true fairy tale in its telling and its development," citing the "marvelous subtlety" of McKillip's storytelling and her "inevitable but unexpected" resolution of the story.

The Forgotten Beasts of Eld has been referenced in Fantastic Literature: A Critical Reader as "we can accept the final transformation of the hideous monster Blammor into the beautiful Liralen bird without necessarily agreeing with the identity of creative and destructive passions that such a metaphor implies.