Pilgrim, the religion overhaul of the Simonrim suite, features a mutation of Morrowind's Divine Intervention, allowing the caster to teleport to a specific temple of the divines (or the Temple of the Divines, in the case of Divine Intervention itself) that can be purchased from their respective priests, which serves as an effective, if expensive, form of fast travel in playthroughs that opt out of traditional "click on the map to teleport" fast travel (such as with Journeyman, natch).

As something of a joke and curiosity, I decided to see how feasible it would be to make a version of that spell for Beyond Skyrim - Bruma's Cathedral of Saint Martin, to give a quick and easy way to return to Bruma on command.

Actually making the spell was simple; getting it to actually show up, however, stunlocked me for the better portion of Halloween.

Neremus Agrecian's merchant inventory has been modified to keep parity with Pilgrim's merchant inventories, offering a plethora of spells, potions, and scrolls, as well as the titular scrolls of Saint Martin's Intervention, dropping you right in the middle of the Cathedral at a moment's notice. Much like the other forms of Intervention, at Expert and above Restoration, you can also purchase the Spell Tome for Saint Martin's Intervention, allowing infinite access to the cathedral.

Astute viewers might have noticed that I mentioned Neremus' merchant inventory, which is notoriously broken and consists exclusively of whatever books he's carrying on his person (which is corroborated by UESP), and has been... not necessarily fixed, but more has been subject to trepanation of the skull.
(This is the part that had me staring at my screen in bewilderment for nearly 6 hours wondering why nothing I was doing was working.)

~Compatibility concerns~
This mod modifies 3 records from Bruma:
xx079E7A <CYRMerchantBrumaNeremusChest>
The merchant chest in the cathedral, which was modified using Solitude's temple chest as a template
xx079E79 <CYRServicesBrumaNeremusVendor>
The faction that is supposed to allow Neremus to actually sell the healing supplies that he claims to be able to sell, which has been modified to use Pilgrim's buy/sell whitelist, and, well...
xx003A1D <CYRNeremusAgrecian>
The man of the hour, the vendor who adamantly refuses to vend. In order to circumvent this issue, I had to... Um... Remove him from his own faction.
The above services faction, as a consequence, is now set to be Allied with the Cathedral faction, and Neremus has been removed from it, as no matter what I (an inexperienced xEdit hack) did him being in this faction prevented him from actually accessing the entirety of his own merchant inventory. This no doubt has a potentially endless stream of negative side effects, but after exasperatedly staring at xEdit for hours this was the solution that finally worked. If YOU have a more elegant solution to this problem, feel free to let me know.
As a result, any other mod that also modifies these records will conflict. My changes are minimal enough in scope that in most cases I would imagine simply allowing this mod to win the conflict will suffice. Mods that alter Neremus' appearance through a plugin will need a patch. Faithful Faces (my overhaul of choice) is strictly facegen and is compatible without needing a patch.