A text compiling various sources of ancient and/or occult lore regarding entities which the author titles 'Elder Evils'. It details several of these entities and the lore surrounding them, as well as theories of their origin, intentions, grand cosmic schemes, and their worshippers.
Pisaethces, known also as The Blood Queen is one such entity. She is believed to be the creator of aboleths, though she feels no such maternal instinct or care for her creations. They, in turn, do not worship her in a way that we understand, but such architecture is built in her honour; with designs of large domed windows of red crystal.
Holashner, or, The Hunger Below. Depicted as part squid, part centipede. Holashner burrows through the depths of the earth, driven by an unending hunger, and leaving behind a black, tar-like substance.
Many of these entities do not have names, as such, rather they are only known by titles given by their cult worshippers, or simply descriptions of the creatures or beings that they are. Thus it is difficult to ascertain whether a source refers to a 'new' entity or an existing one with a new epithet. Sometimes their true name has been lost to eons of time.
One such entity is The World Eater, or That Which Watches from Beyond the Stars/Below the Waves. Sources often refer to it with both titles regarding the sea and stars, so other scholars have theorized that the Watcher from Below the Waves refers to a different entity (Expertise, et al, 1396 IR). There is very little information regarding this entity; as all known sources are pre-Edhilien fall and scarce, or hard to come by. Surviving knowledge indicates it predated known history, being a massive life form that travelled the deep expanse of the Astral Plane, devouring worlds.
Certainly, it must be a being of gargantuan proportions in order to be able to devour entire worlds, and so I posit that The World Eater is not an actual living creature, but a symbolism, a representation of the societal descent of the An Edhil Dynasty in it's late-stages, that led to the fall of the Kingdom.
Charybdis, also known to worshippers as the Duchess, or the Great Swirling Vortex is the entity which some believe is conflated with the previous entry; Charybdis is depicted as a deep-sea monster thought to be hiding in the unexplored depths of the Iapetus superocean. She is honoured by aboleths and sahuagins by including specially crafted deep-sea lanterns designed to work in their underwater lairs.