How did the tritons influence the power balance in Serôs?
Here's what the lore says, drawn directly from the indexed sources:
-106 DR * The surprise return of the hidden triton race from the deep sea trench breaks the strength of Theocracy of the Deep Ones and the morkoths flee back into the deep, ending the Seventh Serôs War. The tritons assist in maintain the balance of power between the morkoths and shalarins in Serôs. * Lorthar of the Waves is killed in battle with an army of elite morkoth warriors in one of the last conflicts of the Seventh Serôs War. The Krakenscourge is taken by the Theocracy, but is quickly reclaimed by the tritons.
Source: -106 DR
-1094 DR * Coronal Merath of Serôs dies fighting sahuagin raiders. * Lynsal, a wizard, son of Merath, becomes coronal of Serôs.
Source: -1094 DR
-108 DR * The morkoth of the Theocracy of the Deep Ones launch the Seventh Serôs War when they assault Es'rath and Hmurrath. They take the Emerald Eye of Kyron, and quickly learn to wield its powers. * Following the devastating Orc Marches in the North, displaced humans return to rebuild Illusk. Once again, it falls under the rule of the Grand Cabal. * The Witches of Rashemen present themselves to the people of Rashemen near Lake Tirulag. This secret order of Raumvirans are dedicated to preserving the lore of the Empire of Raumathar.
Source: -108 DR
-107 DR * During the Seventh Serôs War, the storm giant adventurer Lorthar of the Waves wields the once-lost Krakenscourge.
Source: -107 DR