The Marches of Caetel

The Shadow-Elf core is centre-north on the map. The Gazetteer suggested plot-hooks for exploring beyond, proposing northwest for that. That leaves the northeast.

The map presents the northeast as like Thulingard / Fairbrow northwest: an extension of New Grunland.

The first cavern east of New Grunland starts with "marches". That implies military.

The northern parts of this network lie below the Ethengar Khanate. Those parts are the whole of Caetel (on the map) and Mistpoint, and Targael and Caitros in northern Grunelgard. I assume that the elves haven't bothered digging their way up thence. That's not the elves' military interest.

Above Morkia / Estenreth, south of that, is the northeast "Yellow Orkia" quadrant of Broken Lands. The Bethis mine and most of Grunelgard are below "Darokin" except, that's the Dwarfgate Mountains part, which everyone leaves to Darokin's responsibility just so the elves and dwarves don't have to share a border. Think: the northwest frontier, when British India claimed it.

This suggests that at least the Estenreth cave was orkish (or some other humanoid) before the elves got here. Caetel was that contested ground where the two peoples met. Those relations collapsed in 448 BC when the orcs and hobgoblins got as far as the City. 448 BC is likely when these Marches changed hands.

As of 1000 AC the elves own all three caverns. The elves' military interest here today is defensive - to protect New Grunland. No elf wants the Broken Land surface, nor even its caverns, much less the open-sky Khanate; and it's too much a pain to move agents through these roads to what elves do want, which is Alfheim. Those agents who'd insert themselves to the surface prefer, for their base, the south. From Estenreth the elves maintain cordial relations with Yellow Orkia inasmuch as Yellow Orkia doesn't covet the Estenreth (again?). The caverns are peaceful enough now to rate as a backwater.

To keep it all sleepy and cordial, the central-command military (and not a New Grunland militia) still garrisons that tower Caitros. To this day the military applies "the Caetel marches" or "the Caetel front" to the whole network, even obscure Mistpoint.

This is the furthest edge of the City's writ. We can allow that Mistpoint be larger than the map presents to us, maybe northeast Grunelgard too. The elvish population of the whole network - mines, towns, tower, and whatever lies beyond - maxes out at 3000.