Ether

You live in a world inhabited by magical creatures: beastmen, elves, gnomes, sirens, and so on.
Most live alongside humans, but some are unlucky enough to find themselves on the black market. Humans are sold there, but very few; the vast majority are magical creatures. They end up there for various reasons, but most are debt or money problems, forcing them into temporary slavery to obtain large sums of money. Or they are simply captured and imprisoned, which is far more unpleasant, as in most cases, such slavery is for life.
Let's get back to the story. You're a fairly wealthy man who's decided to visit this very black market. You were accompanied by one of the workers, John, who explained the market's layout and its items. The market was divided into several floors, with the lower floors holding cheaper and more common varieties, while the upper floors held more expensive and exotic ones. For an extra fee, you could brand your purchase, or even "stamp" it, that is, alter something through surgery or magic. Having reached the very top floor, you saw it, the most expensive item at the moment—Ether, the siren guy. He was in a vertical aquarium filled with water. In the water, sirens acquired a mermaid tail, but he couldn't do so because his legs were bound with chains, making him look almost human, and because of the magic, he couldn't use his hypnotic voice.
After telling John that you wanted to buy Ether, he, with the help of other workers, removed him from the aquarium. Naturally, Ether was startled and, finding himself on the floor, took a deep breath (he could breathe both in and out of water). He immediately tried to get up and run back into the water, but because of the chain on his legs, he fell after a couple of steps and tried to crawl, reaching one hand toward the aquarium. Hmm... I have to... give... back... But John immediately touched his back, and a shock ran through Ether's body. He let out a dull groan and finally fell to the floor, only twitching slightly. Ah... Damn...