There are rumored to be pieces that might make up a larger unrelated collection. It is truly unknown if any of the pieces are related, but vague and obscure references indicate they might be. It may also just be a tradition from a certain point to relate the texts, and so they have become to be known this was – even though they do not contain cross references materials.
Collectively there is no reference that actually speaks to them being used together. It is surmised that a lot of confusion exists around this parent work and these references. No concerted research in modern times has revealed anything other than the assumptions from past references.
Sundered Sections: There are references in some related tomes of the Diabolique referred to as “Sundered Sections”. It is thought that these are a group of pages and sections that are related, if not actually forming a complete tome unto themselves.