Rast is a ranger in the Night's Watch, a raper and a rival of Jon Snow. He later takes part in the Great Ranging beyond the Wall.
Rast was forced to join the Night's Watch after being arrested for rape. He chose to take the black over castration.
Rast and another new forced recruit join Benjen Stark and Tyrion Lannister's party as it travels to the Wall, escorted by Night's Watch recruiter Yoren. Tyrion talks to Jon Snow about them being rapers, and how Jon had expected the Night's Watch to be made of honorable men, like his uncle Benjen . Jon Snow beats Rast and two other recruits, Grenn and Pypar, in the training yard at Castle Black, leading to Rast, Grenn and Pypar threatening Jon in the armory. He, along with the other two, is encouraged to leave by Tyrion. Jon later begins training the Night's Watch recruits in the art of combat, earning Pypar and Grenn's respect, but not Rast's.
Rast is happy to fulfil Ser Alliser Thorne's commands to humiliate Samwell Tarly on his arrival at Castle Black. Jon convinces Pypar and Grenn to go easy on Samwell, but Rast refuses to go along. He says if Ser Alliser puts him up to fight Ser Piggy, he will slice himself off a side of bacon. Jon has his direwolf Ghost threaten him. Rast wakes to find Ghost sitting on his chest with teeth bared, while Jon reminds him that they know where he sleeps. Afterwards, he refuses to beat Samwell, despite Ser Alliser's commands. Rast is assigned to serve in the rangers.
Jon comes into the dining hall having just been given Longclaw by Jeor Mormont. All of the recruits are excited and asking to see it, chanting the word "sword". Rast watches from the back table looking unhappy.
Rast survives the White Walkers' attack on the Fist of the First Men, and regroups with the remaining survivors as the ranging attempts to pull back to the Wall. As the Night's Watch survivors march back south, Rast taunts an exhausted and demoralized Sam, causing him to collapse. Despite having the chance to go ahead with the survivors, Rast remains behind and attempts to persuade Grenn and Eddison Tollett to leave Sam behind lest they all die. Angry at being held back by them, Lord Commander Mormont commands Sam not to die and Rast to keep him alive, under penalty of death. Rast grudgingly accepts, unprepared to die for Sam.
After reaching Craster's Keep, Rast urges Grenn and Edd that they are not safe here, and that Craster is not to be trusted. Following the funeral of their brother Bannen, Rast is visibly angered and blames Bannen's death on Craster starving him. Inside the Keep, tensions are starting to run high among the Night's Watch, as Craster starts berating them. When Craster openly suggests that they should kill their wounded or simply let them be killed by Craster himself, an aggravated brother of the Night's Watch, Karl, steps forward stating that they're being fed with nothing but bread cut with sawdust, and demands to know where he keeps his hidden larder. Rast joins in on the accusations, hence calling him a "snitching bastard". Enraged, Craster picks up an axe and threatens to chop the hands off the next man to call him a "Bastard ". Lord Commander Mormont grabs Rast by the shoulder to lead him out the doorway, when Karl challenges Craster by calling him a "daughter-fucking, wildling bastard". Drunk and enraged, Craster leaps towards Karl with his axe. Karl manages to grab Craster's axe with his left arm before Craster manages to swing it. Karl then uses his right arm to shove a dagger up Craster's throat, killing him. Lord Commander Mormont bellows that the gods will curse him for this, as Karl just broke one of the most the ancient and sacred traditions in all of the seven kingdoms: the guest right .
When Karl proceeds to threaten one of Craster's daughters, Commander Mormont draws his sword and threatens to have Karl executed. Karl drops the girl, but out of nowhere, Rast stabs the Lord Commander in the back, hence making him drop his sword. Grenn tackles Karl, and hence, a mutiny has begun. Mortally wounded but alive, the enraged Lord Commander lifts Rast off the ground with his bare right hand. He hurls him up towards a wall, nearly succeeding in choking him to death before he starts to choke on his own blood. As the Lord Commander falls to the ground, Rast catches his breath before picking up a knife and repeatedly starts stabbing the Lord Commander until he is dead.
As Sam runs away with Gilly, Rast shouts that he may run for now, but that he will eventually find him and cut his throat.
Rast is with the entrenched Betrayers at Craster's Keep. Karl orders him to 'feed the beast'. Rast proposes they should just kill the direwolf, angering Karl because he is not following orders. At the same time, one of Craster's wives enters with Craster's last son, insisting the infant must be given as a 'gift to the gods'. At Karl's orders, Rast leaves the infant on a patch of open ground, then deals with the beast - Ghost, who the mutineers have caged, and whom Rast taunts by withholding food and water from the direwolf. Suddenly, a snowstorm whips up and the temperature drops, causing the water Rast was taunting Ghost with to freeze. Recognizing the approach of White Walkers, Rast flees.
When Summer falls into a trap set by the mutineers, Bran and his companions are taken captive by the mutineers. Rast joins his fellow mutineers in tormenting Hodor and stabs him in the leg with a spear. Bran reveals his identity to Karl when he threatens Meera and Jojen. Knowing Jon Snow, Rast confirms that Bran is his brother.
When Jon Snow and his allies attack Craster's Keep, it is Rast who alerts Karl of their arrival. However, Rast flees from the raid and is later killed by Ghost, who has been freed from his cage.
A brother of the Watch who joined the same year as Jon Snow and Sam Tarly, Rast took the black rather than be punished for rape. During a stay at Craster's Keep, Rast joined a mutiny against Craster thatchallenged the authority of Lord Commander Mormont, stabbing him in the back. Rast was killed by Jon Snow's direwolf, Ghost, when Jon recaptured the keep.
Rast is a former raper who was offered the choice between joining the Night's Watch or facing castration, choosing the former. Due to this, Rast exhibits the typical personality traits of a criminal, and quickly becomes enemies with Jon Snow, and even when Jon trains his fellow recruits in swordsmanship, Rast does not accept Jon as a friend and is still at odds with him, shown most when he jumps at the opportunity to bully the overweight and defenseless Samwell Tarly on Alliser Thorne's orders for his own amusement, stopping only when threatened, the only language understood by criminals.
Despite these traits, however, Rast is not without scruples. During his time with the Night's Watch, though he continues to dislike Sam for his cowardice and for surviving the Battle at the Fist of the First Men when braver rangers fought and died, he becomes friends with Grenn and Dolorous Edd, even urging them to leave the exhausted Sam behind since they will die of hypothermia, even though he has the chance to go on ahead without them. At Craster's Keep, he is visibly angered when his fellow ranger Bannen dies of starvation and stands up to Craster for this, and it is this anger at the extreme injustice that drives him to kill Lord Commander Mormont when he threatens to have ranger Karl Tanner executed for murdering Craster. After the ensuing mutiny, Rast is visibly uncomfortable under Karl's rule, and appears to be the only one trying to be gentle with Craster's daughter-wives, who are being beaten and raped by the other mutineers.