I thought fairies did nice things like granting wishes

Artemis is fey (a faery) in the manner that they existed in folklore and superstition before the romanticization that occurred in the 19th century. Prior to that, they weren't depicted as small, sparkling creatures with wings. Rather, they were something to be feared -- easily angered at their best, when not being actively malicious. There are many different varieties of fey, but Artemis is daoine sídhe, the most powerful kind to exist in his world. He belongs to the Unseelie Court, which is the more malevolent one, in contrast to their Seelie counterparts. However, he is genetically half Seelie, and this would be fairly obvious to anyone from his own world due to his hair colour and the nature of his powers.

Artemis is androgynous in appearance, as is standard of fey, though not to the point that it's difficult to discern that he's male. He stands at 6'1" (185 cm), with a lanky but decently muscled build. He's fairly pale, though capable of gaining a tan when in the right environment (Exsilium is not that environment). His ears are long and pointed, with two piercings on the upper side of his right ear. He has a tattoo of runes running up the centre of his back, a thistle on the inside of his right forearm, and a tattoo that I'm undecided about on his left hip.

His hair is golden blonde and straight. It falls to his waist and is usually side-parted and kept in a braid. His eyes are an unnaturally bright chartreuse, with a ring of gold around the pupil. The gold ring reflects light in the way that a cat's eyes do, and the overall appearance of his eyes is supposed to be very disconcerting. His eyeteeth and the ones behind them are longer and sharper than those of a human.

He generally moves with an almost unnatural grace, and carries himself with a great deal of confidence. He will occasionally gesture when speaking, though not on an excessive basis. He is often quite expressive, but has also learnt how to very successfully keep his face blank when he feels the need to hide his emotions.

Even if Artemis is very good at appearing at home in the 21st century, his Victorian upbringing still makes itself apparent in certain aspects of his life, particularly his clothing. He wears well-cut suits on a regular basis. Even when he is dressed more casually, there is still a refined aspect to his clothing, ie tailored shirts and pants, and expensive leather jackets.

If he is ever seen in the clothing that he wears when among the fey court, it has a distinctly fantasy aesthetic. Long, flowing robes are common, though Artemis tends to prefer outfits with pants for the sake of versatility and also because of the amount of time he has spent among humans. Here is one of these outfits, though at his current canon point he doesn't have the armour or sword yet.

In contrast to his androgynous appearance, Artemis' voice is a baritone. He has a very heavy London accent, that sounds rather posh, even if his use of slang isn't always so refined. On rare occasion, his accent will slip into something that sounds somewhere between Irish and Scottish but is overall difficult to pinpoint. When he performs spells, the language he speaks sounds like Gaelic, but is not quite the same and is actually much, much older.