The Swirling Abyss

As you traverse the fog-shrouded southwestern sea, you sense an unusual magic to the south, as if it were beckoning you. Suddenly, the fog lifts, revealing a gargantuan whirlpool swirling in the heart of the sea. Its unnatural size implied one thing: it must be due to some nearby source of magic. You resist temptation and turn back, knowing the peril of approaching it is too great.