The Lost City of Idras: A 12th Level Adventure for 5th Edition

When the gods of law and chaos were destroyed, the divine sparks that remained sought out hosts across Arden. These various hosts eventually became the pantheon of gods worshipped today. A few of the sparks, however, failed to find hosts and crystalized into shards of immense power. There were six shards in all, and if combined, they granted divinity to whoever held them. Unbeknownst to most, however, lesser shards came to be as well. These formed when the weakest of sparks burned out, unable to find hosts or being too weak to assume control over one. Though unable to grant the abilities of a true shard, they still granted the wielder great power... but always at a cost. One such shard found its way to the city of Idras on the western shore of Arden on the Edral Penninsula. 

When the gods smote the elves for their hubris, the city of Idras was mostly spared their wrath. For they had never sought to outdo their creators. Instead, they sought simply to gather knowledge and protect it within the hallowed halls of their great library. When the divine sparks were set loose upon the world, one tried to inhabit the body of the queen of Idras, an elven woman named Selphie Nushalla. As the shard attempted to merge with the strong-willed Selphie, it amplified her desires and made them real. Her desire to protect her people and the knowledge they had accumulated became manifest as a massive shockwave erupted from her mortal form and destroyed the Edral Penninsula, sinking it beneath the waves. When the dust settled, the city of Idras found itself mostly intact, but now sunken beneath the sea where no man, dwarf, elf, or other such creature could ever find it. Her people were changed as well: the elves who called Idras home became the first of the merfolk, merrow, and sahuagin. Queen Nushalla herself was transformed into a monstrous amalgamation of humanoid and fish, doomed to forever guard the power of the shard that now lie embedded in her forehead. 

Centuries have passed since, and the stories of Idras have faded into myth and legend. Sailors often speak of creatures beneath the waves, calling to them from the dark depths, while others tell of fishmen attacking their boats as they cross the sea. Not much attention was paid to such yarns, until one day, when a sailor long thought lost to the waves, stumbled ashore in a small fishing village north of the Great Forest on the western coast of Arden. His skin nearly translucent, and gasping for breath, he told a tale of a city beneath the waves, of horrible monsters within, and a great treasure awaiting any who braved the depths.