Basically, if you dont know what Tartarus is its the equivalent of HELL in greek mythology. It is a location beneath Hades or commonly known as “The Underworld” where the most violent sinners go such as Sisyphus, Tartarus is also a god of some sort being born after Chaos came into existence.
My concept for what it would be in the Arcane Universe is kinda just where Chaos would have the strongest presence similar to the Dark Sea where the deeper you go the more Chaos Energy will be present. (insanity) there would also be villains like Acheron (durza) in the form of a Spirit or Ghost. Maybe some Greek Gods would be down there trapped.
The story its self would come directly from a Journal that got documented by a legendary explorer who I wont name since there is no real relevancy for me to give them a name, The origin of where the Journal came from is unknown but it was found washed up on Shell Island where it was then turned into Juraserva to be studied by them.
If I do end up writing this im thinking about it taking up 1-3 pages of a Google Document with its default font. you can fit about 8404 letters onto a page using only the defaults you were given when you first opened the Document.