The Sapphire Lakes Geographic Location in Kelbonnar | World Anvil

The Sapphire Lakes

Located in the north-west of the Upper Underdark, the Sapphire Lakes are a large lake system known for the strikingly blue colour of their waters, which is amplified by the presence of bioluminescent algae, whose natural light sparkles and reflects off veins of silver on the lake beds and banks. The effect as a whole has led the Sapphire Lakes to be spoken of by travellers and traders of the Underdark as one of the most beautiful places in the whole of the subterranean realm and some claim in the whole of Kelbonnar’s Material Plane.


The Sapphire Lakes are a network of lakes in the northwest of the Upper Underdark whose formation has created numerous peninsulas, small islands and isthmi throughout the region. Whilst in many parts of the enormous cavern in which the lakes are set, the ceiling is over a hundred metres high. In numerous places the height of the ceiling is only a couple of metres above the level of the water, giving many parts of the Sapphire Lakes a grotto like feeling. Whilst the lakes exist separated by strips of land from one another, it is said that underwater passages link all of them together, creating a continuous aquatic ecosystem that spreads for untold miles.   For the most part, the Sapphire Lakes a relatively shallow, with most bottoming out at only 10-15m deep, a depth that appears to the naked eye as far shallower, thanks to the crystal clear waters giving an almost uninterrupted view, save for the aquatic vegetation to the lake bed. However, there are parts where the lakes are much deeper, up to 25m in depth.   Two rivers flow out of the Sapphire Lakes, known respectively as the Major and the Minor Serpent. The Major Serpent flows out of the system to the south, connecting with the Lonely Lake in the southern part of the Upper Underdark, before curving east to eventually join up with the Midnight Marshes. The Minor Serpent flows eastwards out of the system and curves down until it reaches the northern edge of the Eye of Orivious, where its waters plunge down the chasm into the Deep Underdark.

Fauna & Flora

The lake-beds of the Sapphire Lakes are rather verdant, much more so than the rocky landscape that surrounds them, with the bottoms of all of the lakes being carpeted in aquatic grasses. Whilst these grasses are naturally coloured green, the bioluminescent algae that give the lakes their bluish hue grow on the grasses in a symbiotic relationship, with the presence of the algae making the grasses appear a bluish turquoise colour in hue.   There are numerous fish, both benign and predatory inhabiting the lakes, as well as an abundant population of crustaceans, including large beds of fresh water mussels and oysters that thrive around the entrances to the two rivers that flow out of the lakes.

Natural Resources

Whilst there are rich veins of silver beneath the waters of the Sapphire Lakes, the metal is naturally very hard to extract, to the point that it is left alone, as the cost to extract it would be more than the price of selling it. Instead the Sapphire Lakes are known for their abundant supplies of shellfish – freshwater mussels and oysters, as well as freshwater crab and crayfish, which are exported widely across the Upper and Middle Underdark and occasionally even communities on the surface, to grace the tables of the more affluent, or the menus of more well-to-do taverns.


Despite its remote location, the Sapphire Lakes do attract the occasional sightseer from outside of the Underdark, who come to marvel at their ethereal beauty. Generally such travellers are hardy souls, used to roughing it in the wilds or travelling through dangerous places, or are rich enough to be able to afford a large enough escort to keep themselves safe from the many things that would look to make a meal of them.
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Cover image: by Chris Pyrah


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