I would love for someone to make a story or drawing of Sherlock as an Nokken/ Nacken an freshwater spirit.
there most known to take form of an handsome man with glowning eyes, nokken uses his violin that puts people in a trance and lure them into the water and drown them or may play more active role in pulling them in, it is said to be the best musician in the world.
but there not always bloodthirsty and evil, Nokken can also be helpful to you if you give him an offering by his pond, such as three drops of your blood, black animal or brandy he will tune your instrument so it will play as beautifully as his own and become an excellent musician