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. They remind Cyrus of polished river-stones. 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, but for a few exceptions including when he was stung by Whip Spiders and the poison caused him to be almost hyper. Cyrus observes that for the first time, he looks "enitrely like a boy." And Nolan tells him that for a little while the pain will, "...make [him] feel alive." He also displays a nasty temper on several occasions, even throwing Antigone into the whip spiders' den, shortly after she arrives in the Polygon, and is particularly sensitive when accused of theft.
While often seen as cold and reclusive, Nolan displays great loyalty toward the Smiths and the faithful members of the O. of B. His typically flat and sarcastic demeanor conceals what appears to be a noble--if sometimes indignant--spirit. He continues to demonstrate kindness and support toward the Smiths in the face of fierce opposition, showing a willingness to suffer great pain for their sake and his own convictions.
Nolan also likes to eat. This is shown several times during the series when he is mentioned stuffing his face.