Less than 0.1% of the planet’s surface is covered in dry land, most of it scattered swampy islands. More than 50% of the sea is less than 100 meters deep: ideal for nearly world-wide reefs and shallow aquatic habitats to form. Beneath the sun and waves, vast underwater cities of merfolk have been built.
As merfolk they have tails instead of legs and breathe water instead of air, but they still have arms to manipulate tools and are largely humanoid. Most of the merfolk, many of which are well-versed in magic, live in communities built around shared interests. Some are warrior-states that use animated water elementals as soldiers. Others are artisan settlements, crafting splendorous works of art by hand. And others are craftsmen and women who grow shell, coral, and pearl into shapes at an accelerated rate through magic.
This is also how their architecture is formed. Usually eschewing such terrestrial structures as stairs and chairs, they still make use of ceilings and tables. Much of the buildings are some form of storage space for the material culture they craft, trade or display. Only very few merfolk are nomadic.
Considered sacred among the merfolk are large manta rays. It is considered to bring very bad luck to kill a manta ray without performing the proper rituals; otherwise they are kept as livestock. Ranchers herd entire schools of mantas throughout the shifting currents, usually of an easy-to-distinguish plain-bodied breed. Wild mantas, with markings and stripes, are never hunted; merfolk only eat domesticated mantas, if ever.
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