Sandbending Introvert and Ungrateful Brat
Introverted, the quiet, even tortured, poet type. He's very afraid of human emotional contact since the loss of his mentor, and he fears people in uniform due to their implied power. While usually busying himself with poetry or staring at the horizon or thinking about the human condition, occasionally Shen will get a rush of competitive drive, which is like a high to him. When it hits (and it is rare) he revels in the feeling of it, and can become quite cruel. He'll later regret whatever happened in this state, and return to his usual brooding.
The introversion is actually a defense mechanism against his natural curiosity. His mentor had always told him to embrace it, but given the circumstances, Shen chooses to keep it back. He may follow someone with a desperate, hungry desire to know more about them, but rarely confronts them. He thinks life can be viewed safely from afar, and somehow still be experienced.
Around his waist, covered by his vest if he wears it down, is a few sacks of money, herbs, and knick-knacks kept safely encased in sand. He also has a dagger, (poor sand-bender style, as he sold his much more expensive one to survive).
Other than that, he is skilled at basic Earthbending, and even some moderate level stuff, but his real talent is with sand and turning solid rock into sand.
Shen was born to the single wealthiest merchant in the desert. He was reared by eight different maids and various tutors until age eight. At that age, his father discovered he had some Earthbending talent, and sent him to Ba Sing Se to study.
Three years in Ba Sing Se had been the best of his life, living in the upper ring and in general bliss, until he met an old, strong man. His name was Dongyu and had a very abstract way of thinking. For a princely sum he agreed to go back to the desert with Shen as a mentor and earthbending teacher. In the desert, Shen found his earthbending useless, and even though his father would pay huge amounts of money to bring blocks of stone to Shen for practice, he would always use them to make more sand.
Dongyu fascinated Shen, and the nomadic man taught him the value of things and the joy in everyday life. Shen asked Dongyu if he understood sandbending, which he did not. Dongyu, however, told Shen that everything in the world was ultimately made up of the four elements and a few other choice things like love, life, joy, and ambition. Shen was struck by the thought, and started to think very laterally and became a very thoughtful, if not quiet, young man.
His father, worried that Dongyu was trying to turn his son against him, banished the mentor and had Shen taught in private. By fifteen, Shen's hatred for his father had peaked, and he adapted everything he learned to break out of the stone walls of his estate and set off across the desert.
Since then, Dongyu has been traveling the Earth Kingdom, with the intent of going to the Fire Nation. He practices his bending constantly, but his talent is with sand. He feels sand has a distinct power to it, and incorporates all the elements. He has survived for a long time off the money he stole from his father, and his frugality could sicken people. Shen has been absorbed by a sort of creeping depression and loneliness, and rarely eats. He refuses to live off hospitality, but he has no stream of money, and though he has gone for long off the money he despises, it's running out fast, and he's still denying the consequences.
Despite his ultimate goal, curiosity has kept Shen from his task, but he feels he's observing life more closely, and he does not have anything really holding him to his purpose.