Rise of the Kraken

The children of Bajapur tell the story of the Rise of the Kraken, the time a great kraken rose from the deeps in Bajapur's harbour, devastated the city's navy, and demanded a yearly tribute to appease it, and prevent it from scouring the city's docks and blockading the merchant fleets which were the city's lifeblood.
In the year 524 AS (After Sundering), a titanic kraken attacked the harbour. Its tentacles were long enough to reach far ashore, and it dragged several galleons and caravels below the surface of the sea, plucking screaming men and women from the decks to devour. After it had terrorised both the sailors and those ashore, crushing all resistance, its body rose into view, cruel eyes the size of boats fixed upon the transfixed beings witnessing it. Its voice thundered across the water, causing physical pain to those who heard it through the sheer volume and force of it.

These seas and everything that sails upon them are mine. Serve me, and you will live; rebel against me, and you will die. You will send me an offering every year of food and valuables, by sending a laden ship into the deeps to me. If I am satisfied by it, your ships will be allowed to cross my realm in peace.

The peace has held for 473 years, although ships sailing outside of the trade channels must be prepared to make an offering to the kraken to appease it, or risk being dragged down. The ships carry a kraken-priest or an old sailor who knows the ritual, and an underwater horn is used to summon the kraken. If it responds, then its tentacles will arch threateningly high into the sky above the ship, and a chest of valuables will be lowered into a ship's boat and pushed away, toward the kraken. If it accepts the tithe, then the ship is permitted to sail away unmolested.
The children of Bajapur are taught the story as a warning, and to ensure the people always remember the strength of the kraken, and do not grow over-proud and test its complacency.