Nolan, or Nikales, was a boy who stole and ate fruit that would give one inmortality from Gilgamesh of Uruk. To punish him, Gilgamesh cursed him both a thief and a snake. As a side effect of his curse, Nolan is both transmortal and undying. Whenever he gets the slightest wound, his skin peels away, much like a snake's, revealing an unharmed layer beneath. Later in his life, Nolan moves to Ashtown, where he resides in the Polygon. He meets Cyrus Smith and Antigone Smith when they too are sent there, and accompanies them on most of their adventures.
Nolan is described as having "...paper-pale arms knotted with muscle and tied with blue popping veins." He has short, dust colored hair that he crops (albiet unevenly) himself. His eyes, as described by Ben Sterling, are the only thing that gives away his true age, over three thousand years and are a faint green color. The first time he meets Antigone and Cyrus, he is wearing a pair of overly large and pocketed army fatigues and a tight white tank-top.
Personality wise he is described in book two as "...an antisocial transmortal who sloughed off his skin like a snake..." He is almost always bored, except a few exceptions including when he was stung by Whip Spiders and the poison caused him to be almost hyper.
Nolan likes to eal. This is shown several times during the series when he is mentioned stuffing his face.