Mer are as numerous as humans, but since their cities are deep beneath the waves they do not seem particularly common. In many respects mer society is very similar to human society. Mer live in villages, towns and cities. They are grouped into administrative districts that are ruled by Lords, and the Lords answer to the King. The only difference is that mer do not believe in primogeniture. ‘Lord’ and ‘King’ are human translations of mer words, but the positions can be held by someone of any gender.
Mer live for thousands of years and think on very different timescales to humans. A plan put into place today may not come to fruition for another fifty years. The Deep Court of the mer is ruled by a King who remembers the earliest stages of human civilisation. To them, humans are like mayflies, gone in the blink of an eye. The Deep Court rarely speak with humans directly, instead working through Ambassadors from those regions of the ocean that are closer to land.
Mer can take a human-like form, though their skin retains a greenish tinge and fish-like quality. All mer have the power of Illusion. Mer can also express the eight streams of magic, though this is rarer and less powerful than the magic expressed by humans. Mer particularly prize Water and Fire. Water can be used to boost Illusion in the same way that Source can boost the expressed streams.
Mer children are rare and precious. They do not become adults until 80 years of age and are kept far from shore until then to keep them safe.
The mer do not interbreed with humanity. It is said that a young mer prince once fell in love with a human woman. They were happy for a while, but after only fifty years she grew old and died. The prince was heartbroken. They could not bear to live without their love, and took their own life. The King grieved for their child. The mer could not afford to lose children, they said, and from that day onwards relationships between mer and humanity were forbidden.
While this story is extremely romantic it is far more likely that the mer simply have no time for creatures that are barely reach adulthood in their eyes.
Of course there are exceptions to every rule, and there are a few half-mer living secret lives among humanity.