From the Publisher Blurb:
Far out at sea, a mysterious race known as the Myrddin lives in seclusion. Bring them out of hiding and into your game with this first installment of Corners of the Realm, a new series designed to bring exotic races and places into your 4th edition adventures.
The Myrddin are a race of nimble eel-folk that use their electric tongue attack to stun prey and attackers. Though they once lived in rivers on land, they were hunted to near extinction and exiled out to sea. Struggling for survival, they banded together to form giant floating cities from the remains of driftwood and wrecked ships. Come explore what secrets the sea can hold in this new fully loaded supplement, with everything you need to incorporate the Myrddin into the game whether you're on the high seas or not.