Wights are dead men or creatures raised up by the Others, seemingly when touched by the cold that accompanies them.  Anyone who falls against the Others must be burned, or else the dead will rise again as their thralls. Fear of their own dead becoming wights leads the free folk to burn them.
The appearance of wights depends entirely on the condition of the corpse when it is raised. Some are lifelike, while others are badly rotten although the process of decay has been halted. All are easily identified by their eyes having turned bright blue  like two blue stars  and their hands and feet black and swollen with pooled and congealed blood.
Wights are supposedly attracted to warm blood and will attack with surprising strength. Unlike the Others they are slow and clumsy. Wights have a queer, cold scent that can panic animals if they catch a wiff of it. It appears that wights retain at least some of their former memories.
Being dead, wights feel no pain and will continue to fight regardless of injury.  Though they can be stopped by total dismemberment, their limbs will continue to move if detached from their bodies. When a wight is destroyed, the blue disappears from its eyes.
Wights appear to be able to remain in a state of stasis, such as outside the hillside entrance to the cave of the three-eyed crow. The snows have buried most of the dead men, but they remain frozen and waiting.
Dragonglass cannot stop a wight  but fire can. They are highly flammable and will be quickly consumed if set aflame. It is unknown at this time whether wights can cross the Wall on their own, although corpses brought through the Wall can apparently still reanimate as wights. Burning corpses appears to prevent them from being reanimated by the Others to become wights.
A Game of Thrones
Ser Waymar Royce rises as a wight after falling to the Others beyond the Wall and kills Will. Jon Snow rescues Lord Commander Jeor Mormont from the wight which was Othor; the wight seemed to know where Mormont slept and who he was as it tried to kill him.
A Clash of Kings
Othor's still-moving hand is sent to King's Landing in a jar with Alliser Thorne to impress on the Iron Throne the severity of the threat from beyond the Wall so that the king may send more troops to the Wall. Tyrion Lannister keeps Ser Allister waiting so long that Othor's hand decomposes, only bones are left, and is not very convincing.
A Storm of Swords
During the Battle of the Fist of the First Men, the Night's Watch is unable to defend against the wights that are sent against them. In a crushing defeat, the majority of the Night's Watch who fight on the Fist are slain by the insurmountable odds.
A Dance with Dragons
Lord Commander Jon Snow consigns some wildling corpses from a weirwood grove in the ice cells of Castle Black, hoping they can be studied when they rise up. Maester Aemon and Samwell Tarly would have understood Jon's actions, but Septon Cellador is horrified, saying,
Wights are monstrous, unnatural creatures. Abominations before the eyes of the gods. You … you cannot mean to try to talk with them?
Monsters they may be, but they were men before they died. How much remains? The one I slew was intent on killing Lord Commander Mormont. Plainly he remembered who he was and where to find him ... My lord father used to tell me that a man must know his enemies. We understand little of the wights and less about the Others. We need to learn.
Jon Snow later goes down to the ice cells where they have four living men and two wildling dead men, whom he had almost forgotten. He had hoped to learn something from the bodies, but the corpses stubbornly remained dead. When Jon decides to move the living men he instructs Bowen Marsh to leave the corpses. Jon thinks he will need to burn them eventually, but for the time being they are bound with iron chains inside the cells to hold them harmless.
Cotter Pyke sails towards Hardhome by the command of Lord Commander Snow. By rescuing the wildlings Jon hopes to prevent the Others from raising an enormous army of wights by killing the thousands of wildlings stranded at Hardhome and raising them as their thralls. Jon knows that if the Others manage to do this the wights will head for the Wall in their hundreds and their thousands. When Cotter arrives at Hardhome he sends a report to say there are dead things in the woods and dead things in the water.
A list of individual characters that have been turned into wights over the course of the series:
Yet his eyes were still open. They stared up at the sky, blue as sapphires.
The world shrank to two blue stars, a terrible crushing pain, and a cold so fierce that his tears froze over his eyes.
References and Notes
- A Game of Thrones, Chapter 52, Jon VII.
- A Game of Thrones, Prologue.
- A Storm of Swords, Chapter 33, Samwell II.
- A Storm of Swords, Chapter 46, Samwell III.
- A Dance with Dragons, Chapter 4, Bran I.
- A Storm of Swords, Chapter 18, Samwell I.
- A Dance with Dragons, Prologue.
- A Dance with Dragons, Chapter 34, Bran III.
- A Feast for Crows, Chapter 27, Jaime III.
- A Clash of Kings, Chapter 25, Tyrion VI, p 404.
- A Dance with Dragons, Chapter 15, Davos II.
- A Dance with Dragons, Chapter 35, Jon VII.
- A Dance with Dragons, Chapter 39, Jon VIII.
- A Dance with Dragons, Chapter 69, Jon XIII.
- A Dance with Dragons, Chapter 58, Jon XII.
- A Game of Thrones, Chapter 53, Bran VI.
- A Game of Thrones, Chapter 52, Jon VII, p 555.
- A Dance with Dragons, Chapter 28, Jon VI.