The Fortress Eternal and Everlasting

Hm - ok - I'll see what I can hunt up - otherwise we might just fill in the blanks for you here and you can pick the best one you wanna go with.

Nemmiron is the gate-town leading to Arcadia, and Soul's Desire contains a portal to Bytopia. They're located on the same mountain-island that Heart's Faith is. Soul's Desire is on the shore, and has a lighthouse nearby, while Nemmiron is up the slope a ways, and looks much smaller. This is revealed on the map on the last page of the Mount Celestia book in Planes of Law, and the poster map.

The Fortress Eternal and Everlasting is a citadel mentioned on page 12 of the Mount Celestia book and pictured on the map. It's on a different island than Heart's Faith is on, with a different mountain on it, but it's similar to Heart's Faith (with different architecture and government). You can climb up the mountain on that island to get to Mercuria, just as you can with the island that Heart's Faith is located on. From the illustration, the Fortress Eternal and Everlasting might be one of the citadels mentioned that take up the entire mountain-island, being miles long. In the illustration, it takes up the entire peak of the mountain.

There's not much detail on any of these cities, so they're completely open for your development, if you want to. Feel free to decide what kind of government and inhabitants each has. Because they're gate-towns, presumedly Nemmiron is more Arcadian in temperament (with an emphasis on harmony and conformity, and a strong Hardhead presence), and Soul's Desire is more Bytopian (with an emphasis on trade and hard work). Soul's Desire might have some trade with the zoveri and celestial sea elves. It might literally have some role in satisfying the hidden desire of the soul, too, with spiritual arts that no one else knows. Maybe it's ruled by a cabal of celestial mind flayers who have learned to feed harmlessly on spiritual auras instead of brains, who trade with the zoveri for pearls they need to use as psionic focuses. I just made that up. Nemmiron sounds kind of Babylonian to me, so maybe it was founded by immigrants from Marduk who left Arcadia for some reason. Maybe they disliked the anti-dragon bias of Marduk when a member of their family mated with a silver dragon, so they're a clan of half-dragons with a Babylonian culture.

There, that's kind of good. So Nemmiron is Babylonian half-dragons and Soul's Desire is good-aligned mind flayers. The only thing left is to decide what the Fortress Eternal and Everlasting is like. It seems to have a theme of permanence, like something that was created at the beginning of time, or which believes it will stand until time's end. Maybe its inhabitants are living constructs, confident in their immortality, continually repairing themselves with celestial alloys. They probably allow other races to dwell under their enlightened rule, but the constructs are the fortress's rulers. Maybe immediately below them is a caste of half-golems who have replaced some of their body parts with construct grafts, and below them are ordinary humans, aasimar, and dwarves who can't yet afford to become half-golems. How's that?

Coriandor was an elven village mentioned in The Inner Planes, page 119. It contains a portal known as the Crystal Triangle, an almost invisible gate made of glass. Coriandor exists on both sides of the portal, both in Pelion and on the Quasielemental Plane of Salt. They have a circle of magical protection which allows them to maintain a perfectly manicured lawn of grass on both planes, which can animate to kill invaders. The key to the portal is a handful of flower seeds.