The merfolk live in a typically matriarchal society, with mothers and women at the head of the household. Part of this is due to the unequal birth rates of girls vs boys. Girls are much more likely to be born than boys, and thus boys are typically treated as homemakers and house-husbands. 

One of their main customs is the love and celebration of music in all forms. Songs are often carried down through generations as an heirloom. Mothers hum it to their young and teach them to learn their songs as they grow. Merfolk songs and music often spread across the empire in its golden years. Some get legendary enough to be performed by entertainers across many states. 

Tail-Shifting

A common ability for all merfolk is the ability to magically shift their tails for a pair of human legs. This can only be done outside of bodies of water, and they can only shift back when sufficiently wet. When shifting, their entire body's appearance changes too, and a variety of factors can change. Including but not limited to Hair color, eye color, skin color, teeth shape, nail length, and ear shape.

Some features that cannot be shifted away from are as follows: Pointed ears, such like an elf or half-elf, covered gill vents on the side of the neck, body shape/type, hair length, tattoos (they appear muddier on scales but still visible), and scars.

Shifting is a learned trait, and it is mainly learned during adolescence. Some take longer to learn how to shift than others. Some can even struggle to shift certain parts of their appearance, like fins or ears. Some prefer to keep various features, it's all up to you.