The Keeper of the Cage was an enormous once-human monstrosity who dwelt deep within the Dreamlands in Brian Lumley's 1978 novel The Clock of Dreams. As his name might suggest, he was the guardian of a gigantic cage filled with beings who were to be sacrificed to the Great Old Ones.
A colossal, hairless, humanoid creature whose skin had the whitish pallor of the grave, the Keeper claimed to be both near-immortal and near-omniscient. Formerly a mortal man who had been remade by the Great Old Ones after they caught him trying to use their own power against them, the Keeper had been stripped of all self-interest save that required to survive, and posted as a sentry next to the great pit into which their sacrifices were to be cast.
When interdimensional time-traveller Titus Crow journeyed through the Dreamlands his love, the Lady Tiania, was abducted by one of the servants of his enemies, a great Night-gaunt. Following the creature back to its nest, he found her in the hands of the Keeper. After freeing the creatures held in the cage, Crow attempted to do battle with the Keeper but was completely outmatched. Only the intervention of Crow’s friend, Henri-Laurent de Marigny, swung things in Crow's favour, with de Marigny at the helm of a machine outfitted with a weapon of awesome power by the Elder Gods. This weapon made short work of the Keeper and the trio, along with all of those imprisoned in the cage, were able to make their escape.