The Lava Men are a race of Subterraneans living in tribes in underground caverns deep beneath Earth's surface. The Lava Men were originally members of the Gortokians, the first race of Subterraneans cloned and genetically engineered from the cells of human beings many centuries ago by the Deviants. The Gortokians finally successfully revolted against Deviant rule and became independent of them. Eventually a minority of the Gortokians formed a religious cult, which worshipped a demon whose identity has not yet been determined. This demon transformed his worshippers into a new race of Subterraneans who have become known as the Lava Men, and who abandoned the Gortokian civilization. Today there are two known tribes of Lava Men, one associated with the Lava Man witch doctor Jinku, and another, which was nomadic for centuries, but recently established a village in caverns beneath the New York State site of the research facility Project: Pegasus.

Lava Men are humanoid in height and form, but they have red skins of rock-like consistency. The density of their bodies is greater than that of a human being, and they are about twice as strong as the average human male. Lava Men are highly resistant to extreme heat, and can stand in molten lava without harm to themselves. These physical differences between the Lava Men and other Subterraneans are the result of the transformation of the original Lava Men by the demon they worshipped. These changes have been inherited by their descendants.

The demon also gave the Lava Men various superhuman powers, at least some of which are semi-mystical in nature. Lava Men constantly generate tremendous heat, so that the ground is often seen to melt around their feet, and oxidation occurs around their bodies, often causing flame (to which they are immune) to appear around them. A Lava Man can increase the amount of heat he generates, so as to create a sphere-like area of intense heat about himself that will melt a weapon pointed towards him, or to melt a deep hole beneath his feet almost instantaneously. A Lava Man can generate an internal body temperature of thousands of degrees on the Fahrenheit scale. A Lava Man can mystically cause large amounts of volcanic ash to appear seemingly from nowhere or transform metal into volcanic ash. Some Lava Men can mystically transform themselves into sentient giants, over twenty feet tall, composed of hardened lava. Some Lava Men can mystically command molten lava to do their bidding through performing a ritual prayer to the demons they worship. Upon death a Lava Man immediately decomposes into dust.

Lava Men have a primitive tribal culture in which science is virtually unknown. Tribes are headed by chiefs, but great power in the tribes is held by the shamans (sometimes called witch doctors) who are their religious leaders.

The first reported appearance of a Lava Man on Earth's surface occurred when Loki, the Asgardian god of evil, maneuvered the Lava Man Molto into battling Loki's arch foe, the thunder god Thor. However, Thor and Molto parted as friends. Subsequently, against Molto's wishes, his tribe attempted to attack the surface world, urged to do so by the shaman Jinku. However, this attempt was thwarted by Thor and his fellow Avengers. Years later, Jinku persuaded the tribe's chief to have the tribe steal advanced machinery belonging to the Mole Man. Jinku planned to use this machinery to activate every volcano on Earth simultaneously, thereby destroying much of human civilization and leaving much of the surface world ripe for conquest by the Lava Men. Molto went to warn Thor, but was struck down by a blast of radiation from Jinku's staff. Molto nevertheless made it to the surface world and warned Thor and the Human Torch before dying. Thor and the Torch, assisted by the Mole Man's Subterraneans, defeated the Lava Men, and Thor destroyed the machinery Jinku planned to use against the surface world. Still later, people at Project: Pegasus began drilling down into the caverns where, unknown to them, a tribe of Lava Men had established a village. Thinking they were being invaded, the Lava Men tribe invaded Project: Pegasus. However, the Avengers made peace with this tribe, and Project: Pegasus began drilling for magma in another direction instead.

No more than a thousand Lava Men are believed to exist at this time.

First Appearance: (Molto) JOURNEY INTO MYSTERY #97, (Jinku and his tribe) AVENGERS #5, (tribe beneath Project: Pegasus) AVENGERS #236