A race of beings in the Cthulhu Mythos.

'Invisible ones from the stars.'. These latter, he said were definitely aliens on our earth, and the chief among them was called Ghatanothoa, the dark one. They sometimes took forms, such as the monster on the tablet-who was a representation of Ghatanothoa-but existed as 'vortices' of power in their natural state.
-Colin Wilson's The Return of the Lloigor

They are vortices of power in natural form, and completely invisible to human eyes. On rare occasions they can create tangible, visible bodies for themselves. These bodies are monstrous and bear some resemblance to enormous reptiles, though inspection reveals their utter dissimilarity to any reptiles that ever walked the face of the earth.

The minds of lloigor are not divided into layers of consciousness. Lloigor do not forget, nor do they have imaginations or subconcious to mislead or distract them. Their outlook of absolute pessimism results in an atmosphere of gloom that makes lloigor minds and actions incomprehensible to humans. Mind-contact with lloigor always leads to suicidal depression for the human partners.

It is believed that the lloigor originally came to earth from the Andromeda galaxy and that their first earthly colony was on a lost continent somewhere in the Indian ocean, possible the same sunken continent that now bears the city of R'lyeh and its star-spawn with it. The lloigor used human slaves to perform their will, and used inhumanly cruel disciplines to control recalcitrant slaves, such as amputating limbs and or causing cancer-like tentacular growths to sprout on them. Earthly lloigor continued to decay and decline, and they retreated under the earth and seas, where they still husband their failing energies.

Wales, Rhode Island, and Iraq are places where lloigor are known to have acted in recent years. They are hinted at in the folklore of Haiti, Polynesia, and Massachusetts. Lloigor are sometimes linked with the Great Old One Ghatanothoa, now resting beneath the waves of the Pacific, and with Ithaqua.

-Excerpt from Call of Cthulhu, 5th Edition.