My first ritual of cobbled-together Goetia from Verum, The Red Dragon (Grand Grimoire), and a bit of Thelema I performed on Walpurgisnacht many years ago. Ah, good times!
This was long before much better academic research had come out, recently researched from academic sources by Jake Stratton-Kent. But even in the 1990s, when so many pieces were missing, intuitively, it seemed to me that they were all from a similar tradition.
Now we know more of the Cyprianic line of transmission, European diabolism, and the British Cunning Folk—holdovers/modulations from early Goetia, but mostly throughout Asia Minor territories, including parts of the former Greco-Roman Empire, which moved it all into a Christianized mythic framework through the influence of the Byzantine Church.
But an empire now reduced to a regional power in Constantinople, with the Franks taking over the Western Church and making a feral Frankish Catholicism. Friggin' barbarians. I say this with a certain level of admiration. The Vikings converted and conquered Europe under the banner of St. Michael. Beware the Nordmen!