In Volume 1, Book 3, Chapter 7, Gawaine's refusal to have mercy on a knight who killed his hounds leads him to accidentally behead the man's lover. This scene, laced with situational irony, foreshadows Gawaine's eventual role in the civil war that destroys the knights of the Round Table:
‘Thou shalt die,’ said Sir Gawain, ‘for slaying of my hounds.’
‘I will make amends,’ said the knight, ‘unto my power.’
Sir Gawain would no mercy have but unlaced his helm to have stricken off his head. Right so came his lady out of a chamber and fell over him, and so he smote off her head by misadventure.
‘Alas,’ said Gaheris, ‘that is foul and shamefully done, that shame shall never from you; also ye should give mercy unto them that ask mercy, for a knight without mercy is without worship.’
Gaheris takes the opportunity to preach to Gawaine about the necessity of mercy in chivalry, but the irony does not solely lie in Gawaine's failure to act like the knight he is supposed to be. On a deeper, more human level, Gawaine is utterly convinced that killing the knight in revenge will right the wrong that has been done. His rigidity in this conclusion makes him unable to react to further information (either the request for mercy or the sudden appearance of the man's lover before his blade). Ironically, his total confidence that he knows how to right the situation causes him to make everything worse. As Gaheris says, "that shame shall never from [him]" (he will never be rid of the shame of what has just happened).
This moment is formative for Gawaine in that afterwards he must commit himself to defending women, but he does not learn from it as much as he ought to. His ill-fated certainty that revenge will right a wrong foreshadows his reaction to his brothers' deaths at Launcelot's hand. Launcelot kills Agravaine, Gareth, and Gaheris not because he wants to, but because he is cornered. In the case of Gareth and Gaheris, he is not even defending himself, but rather Guenever, who has been sentenced to death. He charges in and kills the people he thinks are going to kill her before even realizing that Gareth and Gaheris are among them. When Gawaine learns that Launcelot has killed his brothers, he is again so angry that the only path that he can see is revenge. His need for revenge becomes one of the primary reasons Arthur escalates the fight against Launcelot to the point that they destroy one another. If Gawaine had learned to suppress his appetite for revenge, the knights of the Round Table may never have fallen as they do at the end of the book.
In Volume 1, Book 4, Chapter 9, Arthur (disguised) holds his own in a fight against Accolon, who Morgan le Fay has equipped with Excalibur. The dramatic irony of the scene helps build Arthur's kingly authority:
Then were they wroth both, and gave each other many sore strokes, but always Sir Arthur lost so much blood that it was marvel he stood on his feet, but he was so full of knighthood that knightly he endured the pain. [...] Accolon was so bold because of Excalibur that he waxed passing hardy. But all men that beheld him said they saw never knight fight so well as Arthur did considering the blood that he bled.
None of the onlookers knows that it is Arthur whom Accolon is fighting, nor does Accolon know it himself. While Arthur is fending off an assassination attempt by his sister, Morgan le Fay, it simply looks like Accolon is a ferocious fighter and that Arthur is outmatched by him. But the fight lasts longer than anyone expects, given that the amount of blood Accolon is spilling should mean that Arthur will lose quickly. He impresses everyone who is watching the fight by continuing to fight well. In fact, Arthur is fighting even better than anyone knows, given that the weapon Accolon is using is Arthur's own magical sword. Even not knowing this, the audience is left wondering how Arthur is lasting so long in this fight.
Also unbeknownst to onlookers, Nimue intervenes in the fight on Arthur's behalf. This finally allows Arthur to get the upper hand, at which point he reveals his identity. To everyone watching, this is a climactic answer to the question they have been asking this whole time. Because Arthur is a king, he is stronger and braver than Accolon. The logic here is circular: Arthur is a king because he is inherently strong and brave, and being a king makes him strong and brave. Still, this is the way many people thought about kings in Malory's day and earlier, especially given the notion that God imbues kings with the power to rule. If anyone had doubted Arthur's fitness to rule before, the resolution to the dramatic irony in this fight strengthens his standing as a king.
There is extended dramatic irony in Book 7 regarding Gareth's identity. The dramatic irony peaks in Volume 1, Book 7, Chapter 33, when Gareth and Gawaine unknowingly fight one another:
[...] Sir Gareth stood there alone; and there he saw an armed knight coming toward him. Then Sir Gareth took the duke’s shield, and mounted upon horseback, and so without bidding they ran together as it had been the thunder. And there that knight hurt Sir Gareth under the side with his spear. And then they alit and drew their swords, and gave great strokes that the bood trailed to the ground. And so they fought two hours.
[...][Linet] cried all on high, ‘Sir Gawain, Sir Gawain, leave thy fighting with thy brother Sir Gareth.’
Gareth does not realize that it is Gawaine charging toward him. He only knows that an armed knight is coming to attack him, so he prepares to charge the knight himself. Although it is common for knights of the Round Table to have scuffles with one another, it is a bit more serious for Gawaine and Gareth to draw one another's blood. They are brothers, so one's blood is also the other's blood. At the end of the book, Gawaine proves especially committed to this idea. He is so angry that Launcelot has killed his brothers that he urges Arthur on to war. If Gawaine knew that he was fighting with his brother, he would likely never have drawn blood.
As soon as Linet reveals each of their identities, the brothers stop fighting and declare friendship. This is an important moment for Gareth because he has been striving for recognition as a man who deserves to be knighted, regardless of his blood or name. Gawaine's recognition that Gareth is his brother only after they have matched each other in battle, and only when someone else reveals Gareth's name, indicates that he is recognizable as a knight even without his name.
In Volume 1, Book 7, Chapter 11, Linet marvels that Beaumains has continued to put up with her berating remarks the entire time they have been traveling together. Beaumains explains the situational irony:
[T]he more ye said the more ye angered me, and my wrath I wreaked upon them that I had ado withal. And therefore all the missaying that ye missaid me furthered me in my battle, and caused me to think to show and prove myself at the end what I was[...]
Whereas Linet and any reasonable person in this world would expect Beaumains to part ways with Linet or otherwise stop her from being so rude to him, Beaumains explains that her cruelty has actually helped him accomplish his goals. He is trying to "show and prove [himself]," which he is better able to do when he can channel anger at Linet into his fighting tactics with the other men he meets.
Beaumains's interest in proving "what I was" in each of his fights hints that there is more to him than meets the eye. As he reveals several chapters later, he is Arthur's nephew. Linet has already joked that he might have noble blood given his obsession with treating even the rudest women according to the chivalric code. The idea of noble blood carried much weight in the 15th century. Malory seems to imagine that it was an even bigger deal in Arthur's day. A person could become a knight through nobility because chivalry (the code knights were bound by) was supposed to be inherent to noble blood. It was much more difficult to be knighted for simply living up to the chivalric code. Beaumains wants everyone to be able to see, like Linet, that he embodies nobility in his character as well as in his name. He wants to earn the title of knight before anyone uses it for him.
An additional layer of situational irony lies in the fact that it is Linet who first glimpses signs of Beaumains's "noble blood." As his constant detractor, it does not seem that she should be the one to see through to his inherent nobility. This irony further supports Beaumains's notion that Linet is not really his enemy at all. Instead, she is there to help him prove himself to the rest of the world.
An instance of both dramatic irony and situational irony occurs in Volume 1, Book 8, Chapter 24. The queen has given Dame Bragwaine and Gouvernail a love potion for La Beale Isoud to share with King Mark, but La Beale Isoud and Tristram unwittingly share it:
And then anon Sir Tristram took the sea, and La Beale Isoud; and when they were in their cabin, it happed so that they were thirsty, and they saw a little flacket of gold stand by them, and it seemed by the colour and the taste that it was noble wine.
Then Sir Tristram took the flacket in his hand, and said, ‘Madam Isoud, here is the best drink that ever ye drank, that Dame Bragwaine, your maiden, and Gouvernail, my servant, have kept for themself.’
The dramatic irony is the most obvious here. The narrator has just recounted how the queen is planning for the love potion to help La Beale Isoud fall in love with the man she is being sent to marry. The reader knows that the wine Tristram sees must be this very love potion. As Tristram and Isoud prepare to drink the wine, the reader sits in suspense, waiting to see what will happen when the love potion cements not Isoud and Mark's love, but rather Isoud and Tristram's.
The love potion incident is also laden with situational irony. The love potion is the perfect plot device to create an obstacle for a more real love affair. Indeed, that is exactly its intended role: it is supposed to supplant Isoud's love for Tristram so that she will be able to marry Mark without feeling unhappy. Meanwhile, Tristram will be left in the dust. Tristram has promised his uncle that he will bring La Beale Isoud back to Cornwall for Mark to marry. Without knowing anything about a love potion to take the edge off, Tristram is already planning to make this sacrifice in the name of honor. But instead of helping ease the pain of the sacrifice to La Beale Isoud (who doesn't seem to have had any choice in the matter), the love potion instead reinforces the love Tristram and La Beale Isoud already have for one another. The potion that was meant to make the arranged marriage easier instead adds the weight of magic to the main obstacle already in the way.
In Volume 2, Book 12, Chapter 4, Launcelot (banished by Guenever from Arthur's court) wanders bedraggled into the city of Corbin. The narrator uses a simile to highlight the dramatic irony of Launcelot's concealed identity:
And when Sir Castor was made knight, that same day he gave many gowns. And then Sir Castor sent for the fool – that was Sir Launcelot. And when he was come afore Sir Castor, he gave Sir Launcelot a robe of scarlet and all that longed unto him. And when Sir Launcelot was so arrayed like a knight, he was the seemliest man in all the court, and none so well made.
Launcelot has been wandering for a while, ever since he was tricked into appearing unfaithful to Guenever. He has lost some of his senses. Between his ragged appearance and his mental state, no one at Corbin recognizes him for the knight he is. Instead, they take him for a "fool." At the time Malory was writing, a fool would have been understood as a kind of entertainer whose performances could provide not only comic relief, but also lighthearted ironic commentary on society and politics. Launcelot is dressed up "like a knight" at the celebration of Sir Castor's knighthood because it is amusing for people in attendance to see a lowly fool in the garb of the "seemliest man in all the court." Dramatic irony adds another layer of amusement for the reader. While the characters really believe Launcelot to be a fool, the reader knows that there is no need for a simile. Launcelot in fact is a knight: to be dressed up like one is to be dressed up like himself.
At the same time, Launcelot is inhabiting the role of the fool perfectly. By donning knight's clothes, he helps highlight the fact that the people at Corbin don't understand what really makes a knight. Knights are governed by a complex chivalric code that their behavior ought to reflect, no matter what they are wearing. Gareth of Orkney, for example, shows up in Arthur's court dressed like a servant and spends an entire book proving that he is an excellent knight before he will reveal to anyone that he is in fact one of Arthur's nephews. The reader who has been keeping up with all of Malory's knights is thus in on another secret that the characters in Corbin are not -- the secret of what makes someone a knight.
In Volume 2, Book 12, Chapter 8, Brisen tricks Launcelot into sleeping with Elaine of Corbin. Multiple layers of dramatic irony in this incident lead to a rift between Launcelot and Guenever when Guenever catches her lover asleep with another woman:
[Launcelot] leapt out of his bed as he had been a wood man, in his shirt, and the queen met him in the floor; and thus she said:
‘False traitor knight that thou art, look thou never abide in my court, and avoid my chamber, and not so hardy, thou false traitor knight that thou art, that ever thou come in my sight!’
‘Alas,’ said Sir Launcelot; and therewith he took such an heartly sorrow at her words that he fell down to the floor in a swoon. And therewithal Queen Guenever departed.
Launcelot has willingly left his own bed and followed Brisen to Guenever's bed, but he does not realize that she has actually led him to Elaine's bed. It is strange to think that Launcelot could not realize who he is having sex with, but this crude joke (a clear example of dramatic irony) is common in literature around this time. For example, the same trope appears in Geoffrey Chaucer's Canterbury Tales, which he wrote in the 14th century.
Launcelot is not the only one who does not know everything. Guenever goes to Launcelot's bed and finds it empty. She tracks him down by listening for the sound of him talking about her in his sleep, something he habitually does. She thinks he is jumping out of bed because he is startled that she has caught him. This is partially the case, but he is also jumping out of bed because he is startled to find out that it is not Guenever in bed next to him. Launcelot does not have time before he passes out to piece together what has happened. Consequently, he can't fill Guenever in on how he came to be in Elaine's bed. Her assumption that he has knowingly betrayed her leads Launcelot to jump out the window and flee the castle when he wakes up. He wanders for two years and seems to lose his mind before anyone sees him again. Launcelot and Guenever both have only partial knowledge throughout the incident, and it leads them to hurt one another.
The dramatic irony makes this incident painfully funny for the reader, who can see exactly how the misunderstanding happened. But on a closer reading, it seems that Launcelot and Guenever each could have avoided the situation anyway, despite Brisen and Elaine's manipulation. Even though the mistaken bedfellow is a common trope, Launcelot might have been able to pay more attention to whose bed he was lying in. As for Guenever, she seems too ready to blame Launcelot for betraying her. After all, she found him by listening to his sleepy ramblings about his love for her. If she had trusted in his devotion and asked for an explanation rather than jumping to conclusions, she could have prevented Launcelot's long absence from Arthur's court. As someone engaged in infidelity herself, Guenever seems all too ready to believe that Launcelot, too, will be unfaithful.
In Volume 2, Book 12, Chapter 10, Launcelot returns to Arthur's court after his long absence, during which he was mentally unwell. Arthur's explanation for why Launcelot "went out of [his] mind" is laced with dramatic irony:
‘O Jesu,’ said King Arthur, ‘I marvel for what cause ye, Sir Launcelot, went out of your mind. I and many other deem it was for the love of fair Elaine, the daughter of King Pelles, by whom ye are noised that ye have gotten a child, and his name is Galahad, and men say he shall do marvels.’
[...]
And therewithal the king spake no more. But all Sir Launcelot's kin knew for whom he went out of his mind.
Among other strange things he did while he was away, Launcelot reportedly struck down 500 knights in three days and called himself "Le Chevaler Mal Fet," or "the knight that had trespassed." Arthur assumes that Launcelot was wandering and losing his grip on reality because he was in love with Elaine of Corbin. This assumption is based on the rumor that Launcelot and Elaine have had a child together, Galahad. Arthur seems to believe that because Galahad is prophesied to "do marvels," the stakes around his conception may also have been high. Compelled by mystical forces to father a child with Elaine, Launcelot may have been driven to a long period of erratic behavior.
Everyone else knows that it is not Elaine, but rather Guenever Launcelot was "out of his mind" for this whole time. Arthur is not completely off the mark: Launcelot's wandering began after Elaine of Corbin and her servant tricked him into looking unfaithful to Guenever. Guenever banished Launcelot, and he jumped out a window. Although Launcelot could be said to have "trespassed" in King Pelles's realm by conceiving Galahad with Elaine, this claim is dubious given that Launcelot did not exactly consent to have sex with Elaine. Launcelot's much more obvious trespass is against Arthur, for having an affair with Arthur's wife. The fact that everyone except Arthur sees this makes Arthur look either foolish or deliberately obtuse. Either he cannot see what is happening right in front of him, or he is trying to ignore it so that his realm can remain stable as long as possible. The dramatic irony here raises the stakes of Arthur's eventual discovery that his favorite knight has been sleeping with Guenever. By that time, the betrayal will run so deep that repairing everyone's relationships will be all but impossible.
In Volume 2, Book 17, Chapter 16, Launcelot wakes up after finding the Sangreal and being knocked out for 24 days for trying to get too close to it. There is situational irony in the revelation of where he has been this whole time:
‘Forsooth,’ said he, ‘I am whole of body, thanked be Our Lord; therefore, sirs, for God’s love tell me where I am.’
Then said they all that he was in the Castle of Carbonek.
Therewith came a gentlewoman and brought him a shirt of small linen cloth, but he changed not there, but took the hair to him again. ‘Sir,’ said they, ‘the quest of the Sangrail is achieved now right in you, that never shall ye see of the Sangrail no more than ye have seen.’
The Castle of Carbonek is in Corbin, where King Pelles first showed Launcelot the Sangreal years ago. It is ironic and anticlimactic that Launcelot and all the other knights have spent so much of the book questing after the Sangreal when it was hidden in plain sight all along. This irony serves two purposes in the book. First it highlights the fact that the quest for the Sangreal was always more about the process of finding it than the object itself. The knights are all faced with a series of tests that they pass or fail along the way, and the results of these tests confirm whether or not they are worthy to "achieve" the Sangreal. The story is an allegory for Christian salvation. "Achieving" the Sangreal, as Galahad will soon prove, involves being taken to heaven by angels. In order to achieve this outcome, Galahad proves over and over that he is pure (which, along with some other chivalric components, means that he has resisted all sexual temptation). The earthly location of the Sangreal does not matter because it is first and foremost a passport to heaven.
The other role the irony plays has to do with Malory's ambivalence toward Launcelot as a hero. Launcelot is a great knight, and he is also, often, a fool who can't quite do the right thing. In this case, the fact that he has been chasing after the Sangreal only to end up exactly where he started undercuts the idea that he is a larger-than-life figure. Malory invites readers to laugh a little at Launcelot, but this comical moment also contributes to the image of Launcelot as a tragic figure. As Launcelot learns in this scene, he has come as close to achieving the Sangreal as he ever will. His flaws (his love for Guenever and his difficulty sticking to the "right" path) mean that he is suited to see the Sangreal but never touch it. In this way, Launcelot represents the kind of heroism that is possible after the death of Arthur. Malory laments the way the world has changed since Arthur's days, and the way the rigid principles of chivalry (which Malory portrays as glorious, for the most part) are no longer attainable. Launcelot is tragic because he embodies the person who strives their whole life for the kind of glory Galahad attains, in a world where such glory is simply unattainable.