Lumbi

Lumbi was said to be the third dwelling of Melkor after he was captured by Tulkas. Gorgumoth, a hound of Mandos, guarded the chained Melkor in the Castle of Lumbi.

In later notes, Lumbi was written as Lumfad.

Other versions of the legendarium
Lumbi and Gorgumoth are not mentioned in The Silmarillion. The event in the books stays the same wherein Melkor was chained by Angainor and cast behind the Door of Night.