The Journal of Monster hunter Alistair Wake has the following too say on Aboleths

“Rarely seen creatures, as they are manipulative and cunning enough to hide behind minions to do their bidding. Aquatic creatures typically living in still fresh water sources like ponds, swamps, and lakes, they carve lairs into the beds of such locations, where pesky airbreathers cannot easily infiltrate their operations.

Aboleths are telepathic creatures, able to infiltrate the mind with ease and deliver messages to its servants from across vast stretches of country side. More horrifyingly they are able to subvert the mind, giving horrible hallucinations that trick victims into doing what the aboleths wishes them too. (Do strong smells impact this like they do The Horned Thing? question to ponder, will do more research).

The mucus they secrete, which tastes overwhelmingly like a rotting corpse, seems to greatly amplify this ability, and is in fact mentally stressing in its own right. Affected victims feel the sensation of drowning, followed by their skin growing cold and clammy, while outside the water, the victim experiences continuous visions of the aboleth that infected it. Its tentacles wrapping around them, words they can’t understand being whispered in their ears, a hazy mirage of a drowned city which they once ruled. Victims seperated from the aboleth and sources of water have been known to scribble madly about their visions through both writing and art. One famous art piece The City of The Twice Drowned, was painted by such a tormented artist. [Editors Note: The section following this is scribbled over, covered in ink splotches, and in one place, blood, only the following sentence remained unscathed] perhaps the artist still sees the city in their dreams at night, I know I do.

By far the most horrifying aspect of the aboleth however, is just how old they are. A single aboleth lives over two thousand years, and an aboleth is able to transfer its memories to its offspring. A single aboleth has memories spanning back to the dawn of time, before even the Forgotten Gods crafted the world from its primordial beginnings as a vast, timeless ocean. They ruled that ocean, and each and every one of them remembers it, each and every one of them remembers exactly who took away their kingdom, and their usurpers who still refuse to acknowledge the aboleths right to rule. They remember being gods, I remember them being gods, I remember what they did to me, you never forget, even once theirs nothing left of them in you, even once you’ve drank enough whiskey to kill an elephant. You never forget, that’s the gift they give you, suppose I should be grateful, who would I be if I did forget?”