The Alamber Sea is the wild cousin to the undersea lands of Seros.
Falling Shelf: The western shore of the Alamber Sea was once a steadily sloping coastline that gradually rose to meet the land of Mulhorand. Millennia ago it is said to have collapsed suddenly following a cataclysmic magical event that has since rendered the entire coastal shelf unstable causing repeated collapsed of the coastline into the sea. Some very ancient texts of Seros imply that the coast of Mulhorand was once connected to the Alaor and the Ship of the Gods in some way.
The exact timing of this great collapse is unknown but is said to have occurred before the Imaskari arrived to claim the lands of Raurin, when only elves and dwarves lived in the land now known as Mulhorand. The largest documented collapse of the coastal shelf of Mulhorand occurred around -1050 DR when roughly 50 miles of land suddenly sank beneath the waves, taking a number of Mulhorandi settlements with them.
The Falling Shelf is largely avoided by the sahuagin and other inhabitants of the Alamber Sea, although Mulhorand claims it is because they claim these waters and keep them free of hostile intruders (a spurious claim at best given their lack of navy).
Akorbil: Roughly 100 miles south, south west of Korinagh, is a strange collection of marble buildings that would not look out of place in one of the triton settlements of Seros, indeed many believe that the fallen obelisks and pillars are proof of early triton settlement in the Alamber Sea.
There are no intact buildings left amid the ruins strewn across the sea bed, except for a partially collapsed steppe pyramidal structure. This structure is known as the Temple of Lost Gods to the Mulhorandi (although they have ironically lost its location). This temple was erected to administer to the worship of those Mulan godkings who have perished over the millennia since they arrived on Toril, it’s only guardian is a lone surviving Divine Minion called Betita Akhabnubis (also a former Divine Incarnation of Anubis) who drives away all intruders from Akorbil and is experiencing strange visions of late from who he presumes is the dead god Anubis.
Ship of the Gods: Named by the Mulan for one of the flying barges that delivered the godkings to Toril (although sages and historians do not know the reason for this association). This volcano has long lain dormant, until approximately 400 years ago when it suddenly became active once more.
The volcanic mountain was once attached to the mainland of what would become Mulhorand, and at that time was settled by dwarves who mined its vast lodes of mithril and constructed complicated machinery that would prevent a catastrophic eruption by venting lava into the Alamber Sea periodically. This machinery was gradually damaged by subsequent tectonic instabilities and pressure is now building (temporarily released by the big eruption 400 years ago) up to a catastrophic eruption.