He hails from a modern or slightly futuristic alternative earth where people with magic/psychic talents exist, but are not particularly organised. He is one of them, and believes that he needs to keep his real name secret to protect himself against not entirely benevolent colleagues.
His author is not entirely sure about his personality yet, but figures it will emerge in time.
His nickname first emerged because he wears only grey (or black or white).
Last seen wearing black sneakers, black jeans, grey sweatshirt with a black dragon design printed on it, and a small messenger bag (grey with black piping; format big enough to hold A5 sketchpad, but not much bigger)
In the long term he was probably aiming at a career in the field of illustration and/or design, and can draw reasonably well. To a lesser degree he has experience with woodcarving.
Grey's magic works through signs. He can produce short-term effects by drawing/writing something, eg on a wall with pencil or on sandy ground with a finger, and charms with longer lasting effects by carving signs in a matrix of wood or plastic, sometimes combined with a knick-knack that fits the purpose.
Short-term effects can last from a few minutes to a day, long-term effects can last up to about a year, though a few weeks is more typical.
The effects of Grey's magic includes various relatively subtle effects (raising or lowering the termperature in a small area by a few degrees, keeping off mosquitoes provided you don't walk into a thick swarm, averting tension headaches, and many more) as well as simple illusions ("make that wall with a niche in it look like it were plain"), the latter being rather difficult.
The drawing of signs/runes/symbols is merely a way for Grey to channel his talent; the designs have no power in themselves. That means if someone else copies them, nothing happens. However, he relies on them so much that he's unable to produce any effect if he cannot leave a mark on a surface.
The symbols he uses are a mixture of ones he uses habitually, and improvised ones that "seemed like a good idea at the time".