Harborwatch, a rugged town built along jagged cliffs, faces destruction as a sea beast known as the Maw of the Deep rises from the abyss to strike at every solstice. Centuries ago the Tide Wardens bound the Maw with the Seal of Aegir, a ritual artifact shattered into four relics scattered across dangerous waters. The party must locate the relics and reforge the seal at the Temple of Tides beneath the harbor to imprison the beast again. Time is tight: a rare celestial alignment will loosen the seal unless the relics are restored and the rite performed before the next high tide. Main quest: gather the four relics, restore the Seal of Aegir at the Temple of Tides, and banish the Maw before the final surge. Locations include Harborwatch, the Sunken Cathedral beneath the docks, the Glass Reef, Ember Crag, Windward Lighthouse, and the Temple of Tides. Plot hooks: a Tidewatch festival is near and the mayor begs adventurers to safeguard ships; a smuggler ring uses relic fragments as power sources; a singing tavern maid hints at forgotten wards; a kidnapped mapkeeper holds key directions to the Sunken Cathedral. Adventure arcs: Act 1 involves investigation and clue gathering; Act 2 covers relic retrieval through underwater exploration, reef dwellers, lava tubes, and haunted towers; Act 3 centers on the ritual at the Temple of Tides requiring a vow or sacrifice, and a final confrontation with the Maw. Challenges include hostile weather, underwater ruin puzzles, diplomatic talks with merfolk and storm spirits, and a moral choice about sacrificing something personal to empower the seal. Rewards include the Blessing of Aegir granting limited water breathing and minor control of currents; attunement to the relics; sea themed magical items; and renown as the saviors of Harborwatch.