The Great Old One

● "Phaedra has been in hiding, collecting everything she needs to punish the humans and rule the seas! Fortunately, Brynn and her mer friends are hot on her trail. Along the way, they'll confront a flurry of toxic jellyfish, confounding clouds of depressing magic muck, and an ancient legendary giant known as "Crabfoot." Brynn, Jade, Will, and Priscilla have sharpened their mer-magical abilities, but soon they realize they'll need help from seafolk and landfolk alike. Will the four friends unite merfolk, dagons, selkies, and humans in time to stop the Great Old One?" ― quoted from this book's Amazon product page as of 2022-02-04.