Merfolk are an amphibious race, born and at home in the water but comfortable on dry land. Humanoid in form, they have skin of ivory, silver, russet, blue, or deep purple. Long fins extend from the backs of their forearms and calves, and their fingers and toes are webbed. The hairlike growths on their heads are either thick and bristly like the needles of a sea urchin, or long and wavy, resembling fine seaweed. In either case, these growths typically range in color from red to warm brown to black. Male merfolk have similar growths extending down from their cheekbones.

Plane Shift - Ixalan

The River Heralds are merfolk—a race of amphibious humanoids at home throughout the oceans, rivers, and rain forests of Ixalan. They stand between seven and eight feet tall, with skin that ranges from deep burgundy through many shades of violet and blue, to green, bright orange, and yellow. They are humanlike in shape, but have long fins extending from their shoulders, forearms, middle backs, and calves. Frills of fins also protrude from the backs of their heads. All merfolk can breathe air or filter oxygen from the water, and they can walk on land or swim with equal ease.

Plane Shift - Zendikar

Curious, thoughtful, and analytical, the merfolk of Zendikar are natural scholars and explorers. In the past, merfolk society was organized around their belief in three deities. But in the wake of the reappearance of the Eldrazi, the merfolk have realized that their faith was a web of lies, built on a corrupted memory of the Eldrazi titans handed down from generation to generation. In peaceful times, the merfolk might have fought over the ultimate meaning of this revelation. But faced with the danger presented by the Eldrazi broods, the merfolk have largely set aside their differences and joined together in a united force. Old grudges still linger, but the well-being of the merfolk race—and the world—far outweigh any ancient conflicts between creeds.

Merfolk are associated with knowledge, logic, and strategy, though the traditional merfolk creeds express this connection in different ways.