Like the Severn Valley, this is an original scenario. Unlike the Severn Valley, it can't be trivially broken out of the campaign and run independently. (As designed, it really lacks any sort of conclusion: The PCs come to Axum, poke around, learn some stuff (that's mostly meaningful in terms of the larger events of the campaign).
If you wanted to run it as an independent scenario, you'd probably want to have a stronger conclusion focused on the Obelisk itself in some way. Did Frumentius remove something from the Obelisk during its destruction? If so, the PCs might need to race the Emporium of Bangkok Antiquities to retrieve it.
Or the EBA might already have it, in which case the scenario becomes about them triggering something horrible with the Obelisk itself. Maybe one of them enters the Obelisk and is horribly transformed by it. (You could pull some of the lore books form the Los Angeles cult concerning Gol-Goroth and his obelisks to help establish some of this conceptually.)
Of course, you'll also need to figure out some sort of independent hook for getting the PCs involved. Maybe they've been hired by the Italian government to prep the Obelisk for looting and, when they arrive onsite, they find the EBA already ensconced?
PDF Link: https://www.patreon.com/posts/2699232/attachments/144939
Props: https://www.patreon.com/posts/2699232/attachments/144940