Caves of Balor

"It can only be found in the caves deep beneath the Forest of Balor."

- Gaius to Arthur about the Mortaeus flower

The Caves of Balor are a vast underground structure located beneath the Forest of Balor. They are populated by Balorian Spiders and are the only known habitat of the Mortaeus flower, which grows on the roots of the Mortaeus tree.

History
When Merlin was dying of a deadly poison, Arthur ventured into the caves to retrieve a Mortaeus flower needed for the antidote. He was accompanied by the sorceress Nimueh, who was posing as a lost, runaway servant and later betrayed him and left him for dead. Fortunately, Merlin's guiding light led Arthur out of the caves before he could be killed by giant spiders (The Poisoned Chalice).

Trivia

 * The caves are likely located in a country called Balor, as the forest above the caves is known as the Forest of Balor (The Poisoned Chalice).