From the back of the book:
Blackwater’s influence is subtle, its progression insidious. This makes it all the easier to see this threat as nothing more than a bygone peril, buried in unfathomable depths. And you’d better believe that’s what aberrations want you to think.
Even as the adventurers possibly live in ignorance of Blackwater’s very existence, strange incidents, murders, and disappearances put them on the trail of an evil all the more pernicious that it subsumes those who fail to vanquish it. To thwart the threat of the aboleths and their mindless puppets, a mind shielded from comforting lies will prove as necessary as a well-sharpened blade.
Aboleths of Blackwater is a collection of five adventures intended for characters of levels 1-7, powered by the rules of the 5th edition of the most mythical role-playing game.
Standalone. The adventures featured within can be played as one-shots or easily slotted in a long-running game, whether for a short autonomous session or as part of a campaign delving into the lore of Blackwater.
Ready to play. The adventures of Aboleths of Blackwater require the Adventurers and Grimoire books (or any other core book containing the 5th ed. rules) to be played. No other resources are necessary: all featured perils, creatures, optional rules, and magic items are described in appendices.