The Eater of Souls was a mythological creature in Vulcan and Romulan cultures, the belief in which originated on Vulcan before the age of Surak and the Sundering. The Eater of Souls was said to devour the katras of those Vulcans who were out during the midday heat.
The early pre-Romulans during the Exile believed that they encountered the Eater of Souls when they were deceived by a planet sized entity that consumed the mental energies of the crew of two ships. This entity may have been the Iruhe, which itself was believed to be the Intellivore creature. The creature's impact on Romulan culture faded over time, due to the fact that Romulus did not have the desert environment of the Vulcan homeworld. The Eater of Souls became a myth most often invoked to scare children, though poorer Romulan families were known to purchase protective amulets to ward away the creature.
The phrase "T'kal ni narak alat N'garkar ack" translates as "Midday sun, Soul Eater come".
(TOS novels: Vulcan's Forge, Vulcan's Heart, Vulcan's Soul: Exodus, Exiles).