The Moon Pool & The Metal Monster

"The Moon Pool" deals with an advanced race which has developed within the Earth's core. Eventually their most intelligent members create an offspring. This created entity encompasses both great good and great evil, but it slowly turns away from its creators and towards evil. The entity is called either the Dweller or the Shining One.
"The Metal Monster" - Dr. Goodwin is on a botanical expedition in the Himalayas. There he meets Dick Drake, the son of one of his old science acquaintances. They are witnesses of a strange aurora-like effect, but seemingly a deliberate one. As they go out to investigate, they meet Goodwin's old friends Martin and Ruth Ventnor, brother and sister scientists. The group is saved from death in the mountains by a magnificent woman they get to know as Norhala. They are led to a hidden valley occupied by what they name "The Metal Monster", a strange metal city occupied by the metal animate Things Norhala commands. This city is governed by what they call the Metal Emperor, assisted by the Keeper of the Cones.

Abraham Grace Merritt (1884-1943) was an American Sunday magazine editor and a writer of fantastic fiction. The Science Fiction and Fantasy Hall of Fame inducted him in 1999, its fourth class. Merritt's novels and stories typically revolve around conventional pulp magazine themes: lost civilizations, hideous monsters, etc. His heroes are usually gallant Scandinavians, his villains treacherous Germans or Russians and his heroines often virginal, mysterious and scantily clad.