* AlternateCharacterInterpretation: The whole book does this to numerous characters as opposed to their traditional portrayal. Also, Derfel very grudgingly admits at one point that his personal view of Lancelot could be clouding how Lancelot comes off in the story
* {{Anvilicious}}: '''RELIGION IS BAD''', and '' '''Christianity''' '' in particular is ''evil''. The message is about as subtle as a sword to the face, and starts being thrown at you from the very first page. This becomes more understandable once one factors in [[FreudianExcuse Cornwell's troubled background]] (adopted by an abusive family who were part of a small Christian sect) which only became public knowledge years later. However, like all Cornwell's work, it does take care to show a few examples of the GoodShepherd.
* CompleteMonster:
** Gundleus is one of the first villains of the series. Initially sworn to Uther, Gundleus is wicked and ambitious and has no intent of honouring his vows to serve the High King's infant grandson Mordred. After Uther's death, Gundleus approaches the baby with its young mother and then murders her after demanding she kiss his sword for protection, before stabbing the infant as well (unknown to him, the infant Mordred was swapped out with a decoy). He then proceeds to rape Merlin's disciple Nimue in retribution for her attitude towards him and rips out one of her eyes for spite. Even his affection for his lowborn lover is shown to be a farce as he abandons her when he gets a better betrothal offer.
** King Dwirnach of Ireland is a vicious tyrant aiming to conquer and kill. What sets Dwirnach apart from the other warlords of the series is his love of ColdBloodedTorture as a hobby. Dwirnach prefers to take his enemies alive, so he can spend his time slowly flaying them. He even keeps the skins as perverse trophies and threatens to both rape and flay the hero Derfel's lover Princess Ceinwyn solely to satisfy his lust for pain.
** King Mark of Kernow is well known for marrying much younger women [[TheBluebeard and killing them later when he's tired of them.]] When one of his betrothed, the young Isolde, escapes with his nephew Tristan, Mark hunts them to Arthur's lands and demands satisfaction. Unable to break the peace [[ToBeLawfulOrGood Arthur is forced to compromise his morals]] by allowing Mark's "justice", forcing Tristan to engage in a fight he cannot win against Mark's champion who reluctantly kills him. With Isolde back in his clutches, Mark immediately has her burned alive on the beach by where her beloved died before returning to Tintagel with smug satisfaction to continue his practices.
** [[AdaptationalVillainy Lancelot]] has no redeeming qualities whatsoever. [[VillainWithGoodPublicity While he pays bards to sing of his brave deeds]], he is actually a Main/DirtyCoward, and a vain and boastful one. When [[spoiler: Benoic is conquered by the Franks]], he does not fight at all, but he still paints himself as the hero. Determined to become king, he first obtains the throne of Siluria and then that of the Belgae, but he decides it is not enough and [[spoiler: he allies himself with the Saxons, Bishop Sansum, and his own lover Guinevere to take the crown of Dumnonia. He desecrates Norwenna's corpse to "marry" her to strenghten his claim and tries to have both Arthur and Mordred killed, although he fails]]. He also rapes Leanor, Galahad's lover, and tries to do the same to Ceinwyn, [[spoiler: sending his minions Dinas and Lavaine to threaten her daughter Dian if she tries to resist, which results in the child being killed. After his plot is discovered and he is defeated, he leaves Guinevere as prisoner to Arthur, which could mean her death]], prompting her HeelFaceTurn. He then [[spoiler: takes refuge with Cerdic's army.]] Eventually his actions prove too much for even his cousin [[TheDragon Bors]], [[EveryoneHasStandards who is a bit more honorable]], [[HeelFaceTurn to stand by his side.]] [[spoiler: At least he gets what he deserves after the battle of Mynydd Baddon.]]
* EnsembleDarkhorse: Sagramor the Lord of the Stones is one of the more memorable and popular characters due to the interesting twist on the "black knight" concept i.e. him being a black TokenMinority (an African veteran of the Roman military who ended up in Britain as the Western Roman Empire collapsed) and hilariously feared by Arthur's enemies just because of it, and being a stone cold badass to back it up, despite getting less focus from Derfel's point of view than the likes of Galahad, his closest friend among Arthur's men.
* SugarWiki/HeartwarmingMoments: A good number.
** Ceinwyn breaks off her march to the altar where Lancelot is waiting to embrace Derfel, saying she will not marry any man, but she will be his wife in all but name.
** Before the Battle of Mt. Badon, Aelle is surprised to hear that Ceinwyn is there with Derfel's daughters and tells the Saxon army to wait while Derfel and Ceinwyn introduce the girls to their grandfather. He then gives Ceinwyn a talisman and promises to safeguard her and the girls if they come with him. She smiles and tells him to take his army home and visit her and the kids every year.
* {{Narm}}: A ''church'' produces a JumpScare in ''Excalibur.''
* OneSceneWonder: Merlin has relatively little time directly interacting with Derfel in the books, but boy does he know how to make it memorable.
* RescuedFromTheScrappyHeap: [[spoiler: Guinevere, whose failed attempt to put her lover Lancelot on the throne is the climax of ''Enemy of God'', redeems herself in ''Excalibur''.]]
* TearJerker:
** [[spoiler:Dian]] being killed.
** [[spoiler: Tristain]] being made to fight King Mark's champion. He knows that he doesn't stand a chance.
** [[spoiler: Cuneglas']] death about half way through his fight with Liofa. He realises he can't win but still sends his men away when they try and rescue him because he knows he has to do it himself.
** [[spoiler: Aelle's]] [[SuicideByCop forcing Derfel]] to finish him (so he can die a warrior's death) is quite touching.
** And, of course, pretty much everything about Camlann.