The Grail-Lands

In the Helionite Faith, Sepitumus the Savior of Mankind is revered above all other humans, but a largely ignored part of his canon, is his journey into the unknown lands (believed to have been Talanthia), where he was blessed by The Lady, a blessing that took its form by the Lady permitting him to drink from her most sacred waters, using a particular cup known as the Grail - and the people of the Grail Lands believe that this took place in their lands.

Touissaint
When Talanthia was first settled by the people from the Westerlands, there was little interest in Touissaint, but it became heavily settled by fleeing serfs and nobility from Dussante, and remarkably, the locals who already lived in the region had already heard of Septimus the Savior, and they spoke of a powerful man who came through the lands from the North, in search of the Sacred Lake, and her Ladyship, and thus they built a city there, dedicated to Septimus, the All-Saint (essential a direct translation of the name "Touissaint").
 * The capital of the City-State is the Citadel of Beauclair, which is named after the the legend, that Septimus visited a Buckle-maker and had him fashion a Chalice out of some metal, which the legend says hardened to the point of being unbreakable after the Buckle-maker had worked it over - the legend, in other words, claims that it was in Beauclair that the Holy Grail was forged by a lowly Buckle-Maker.
 * Touissaint is the leading faction of the Grail-Lands, which are all individual Duchies, tantamount to City-States, but Touissaint has effectively agreed to a condition joining with Karesh, though remaining and Arch-Duchy with the remaining Grail-Lands remaining forever, Vassals of Touissaint.
 * Before Touissaint was essentially taken over by Dussanteans, it was already a trade-hub for the local indigenous people of Talanthia, who used the river-ways to trade.
 * It remains a sort of gate-way into the Talanthian City-States - or an exit.

Redania
Redania was last to join the Grail-Lands, but was liberated by a peasant revolt, lead by a few questing Templar-Knights who had discovered that the Eternal Flame burned in the City of Novigrad. Novigrad
 * The Flame was significant, because it was, in the legend, where Septimus took the Sun-Stone and had it melted into a an actual piece of metal, that he was to forge the Holy Grail from.
 * Novigrad is the capital of Redania, and very impressively, Redania is also home to Oxenfurt, an independent City.

Novigrad is one of the largest cities in Talanthia. The City was originally centered around The Eternal Flame, which the Mage-Lords kept secret for a long time, referring to it simply as "the Spell-Forge of Novigrad". The Old Town of Novigrad, which is now the inner city district, was the whole city at one point, and once Novigrad transitioned from being a seat of importance and

Kaedwen
Kaedwen was settled by Eiferwith refugees from Avalon, and has always remained something of a Frontier. It was no surprise, and no great loss either, when they joined the Grail-Lands. It was, however, supposedly in Kaedwen that Septimus found the Sun-Stone, and since then, many have searched for Sun-Stone fragments there.
 * The Eiferwith were too difficult to manage as subjects, so even the Talanthian Mages did not want to rule it, and it never did liberate itself in any great detail. They just stopped paying taxes to the local Mage-Lord, and he eventually moved away.