An evil monster who inhabited a cave in Fairy Land. He talked visiting knights into killing themselves by convincing them that their lives were too miserable to go on living.
One knight, Trevisan, escaped from Despair and encountered the Red Cross Knight. Seeking to slay the monster, the Red Cross Knight visited Despair’s cave. Despair reminded the Red Cross Knight of his failures and nearly lured him into suicide, but Una, the Red Cross Knight’s amie, intervened and took him to safety.
Source
The Faerie Queene | Edmund Spenser, 1570-1599