He is a wildling and a warg who can assume the conciousness of an eagle he uses for reconnaissance.
While the massive host of the Free Folk marches out of Skirling Pass through the Frostfangs, Orell scouts the Fist of the First Men by warging into his pet eagle. He discovers dead "crows" - the result of the Battle of the Fist of the First Men
Orell is among the party that reaches the Fist of the First Men alongside Jon Snow and Mance Rayder. Here they encounter the bloody aftermath of assault on the Night's Watch by the White Walkers and their army of undead Wights. Except for corpses of horses, there is no sign of any human corpses - which Orell had seen when he scouted ahead earlier by warging into his eagle
While climbing the Wall, a crack within the ice causes an avalanche. Losing their footing, Orell yells to Tormund they must cut Jon and Ygritte's rope. Orell eventually cuts the rope, and Jon is able to swing Ygritte and himself to safety before it snaps
When a horse breeder is chased by the wildling party, consisting of Ygritte, Tormund, Jon Snow and others, they manage to successfully capture the man. As Tormund is about to murder the breeder, Orell intervenes and says that the "crow" should do it. Jon walks forward and presses his sword against the man's jugular, but stops the murder and shoves him away, only to be shot by Ygritte. Orell shouts and claims that Jon always was a "crow" and a battle ensues. After a few moments of sword fighting, Jon shoves his sword into Orell's chest and whispers "You were right the whole time", before pulling it out and leaving Orell on the ground to die.
Orell manages to cheat death, however, warging into the mind of his eagle with his dying breath. As Jon stands over Orell's dead human body, Orell's consciousness controlling the eagle's body attempts to exact revenge by clawing at Jon's face with his beak and talons, but Jon is able to fight him off.
A wildling scout and warg, Orell traveled with an eagle. He was always suspicious of Jon Snow's loyalties to the wildlings, and was eventually proven right. Jon killed Orell, but not before the scout warged into his eagle.