* Lief means [[spoiler: "heir"]]... and "loved", of which he is both.
* After Doom [[NonSequiturThud hits his head and is rambling about his history after leaving Del]], he uses the phrase [[spoiler: "dear heart"]], used [[spoiler: by Jarred to Anna in Part 1 of ''The Forests of Silence'']], subtly hinting at the truth that [[spoiler: he is not Endon, as the scene implies, but Jarred]].
* The behavior of the different Pirran tribes is consistent with the kind of music they liked. The Plumes, who liked brave and glorious music, were willing to stake everything on letting the companions try to kill the Fear. The Aurons, who liked the beautiful and rich music, had a schism over the meaning of beauty in their changed circumstances, and many of them shut themselves in a magic dome to uphold their ideal of beauty, rather than face reality. The Kerons...well, it works for the first two, anyway, and they didn't spend much time around the Kerons in any case.
** The Kerons liked mysterious and mystical music, and had stronger magical abilities than the other two groups.
* All the first series main villains represent a different sin:
** Gorl: Wrath, which pushed him into killing his brothers and ruining the forest.
** Thaegan: Lust. Just look at how many children she has. Plus, cruelty is taking pleasure in the suffering of others.
** Reeah: Vanity. It becomes his FatalFlaw as he's too much busy gloating to notice Jasmine.
** The Hive: Greed, obviously.
** Gellick: Gluttony. He enslaved the Dread Gnomes, forcing them to farm flies for him and killing them if they couldn't replace the flies he ate.
** The Glus: Sloth. It's a huge slug that can't move very fast, and it lives in a cave network where resting for too long will kill you.
** The Guardian: Hubris. He's powerful and dangerous, but he believes that he's too great to be bested, so he plays games with his guests and eventually is defeated.
** The Shadow Lord himself: Envy. He hates all "good" living beings, and wants to rule everything, ''especially'' Deltora, which was snatched from him multiple times. Plus, if he can't have it, [[ThePlan well…]]
* In The Deltora Book of Monsters it is revealed that [[spoiler: Josef hid the book The Belt of Deltora where he hoped someone would one day find it, namely Jarred or Endon.]] It is said that Jarred started it all, because he found the book and hid the royal family, but without Josef Jarred would not have been able to find and The Belt of Deltora at all, and thus come to realise as he did the dangers the Rule posed on the royal family and the safety of Deltora.
* (Also doubles as Fridge Horror) Throughout the series it often states that the characters, Lief in particular, cannot look away from a horrifying sight. At first, this seems like nothing more than shock. Then, you read the eighth book, and about the Place of Punishment, where executions and tortures are carried out, while the rest of the population, including babies, are forced to watch under threat of death. The reason why Lief doesn't look away is not out of shock, but because he has been conditioned since birth to watch.
* At the very end of ''The Towers of Illica'', Sky gives Britta an odi hairclip for her to use to win the Rosalyn Trust competition (though he passes it off as a trade to fulfill the contest's requirements). The odi on the hairclip are arranged into a pattern meaning 'forever'. Britta also recalls text from A Trader's Life which state that odi ornaments are often prized as love-tokens because "their shells are so rare and their marvellous colour, '''blue as the eternal sky''', never fades". [[spoiler: This could be a blatant foreshadowing of romance between Sky and Britta.]]
* The entire struggle against the Shadow Lord (and, in the third series, resisting the temptation of evil) can be seen as a metaphor for dealing with depression and anxiety. Overcoming despair is a recurring theme throughout the series, the effects of the Shadow Lord's crystal and the Sisters bear resemblance to the symptoms of a panic attack, how the Shadow Lord can only be repelled and never truly defeated may strike home to those dealing with mental health issues, etc. It helps put the EsotericHappyEnding in perspective: the point of the ending isn't necessarily that the Shadow Lord is (temporarily) gone, but that everyone went on to live fulfilling lives in spite of everything. It's particularly notable for Lief, as he nearly crossed the DespairEventHorizon and doesn't seem to explicitly get better (especially regarding his issues as king)--however, it's implied when he and Doom discuss [[WoobieDestroyerOfWorlds what drives a once well meaning person to evil]] and Lief, now able to empathize, simply states that other choices can be made.
* The Shadow Lord based most of his plans and traps on legends or things that actually happened. Considering that he faked a [[spoiler: sister for Jasmine]] means that [[spoiler: Anna]] might have been unknowingly pregnant when she was killed.
** On another note, think carefully about the Ols. Supposedly, there's various tests to see if the people you think are on your side are really Ols, primarily the three-day test. But this doesn't work for higher than Grade 2 Ols. At any slow moment when Lief has his guard down and thinks the Shadow Lord's threat is over, the Ols can sneak in, replace Jasmine or Barda, and kill him off in his sleep. In a deeper level, how can you trust ''anyone''? Even if they aren't Ols, the second plan of the Shadow Lord is mind control snakes. ''Anyone'' can be working for the Shadow Lord.
*** In fact, consider the Ol which was impersonating Barda in Maze of the Beast. It could have quietly killed Lief and Jasmine anytime during those two days which they travelled together, even in their sleep. Luckily the Ol had orders to deceive rather than kill...
** All of the mind control snakes were killed in the end of the second serial. Of course, the Shadow Lord can grow more, but without a pool of Deltorans he can send back to infest others, it'll be a lot harder to do anything with them. As for the Ols, it's a problem. But it's possible they can't even get into Deltora with the Belt at its full power and the Sisters defunct.
* Doran's fate. Hundreds of years [[spoiler: as the guardian of the Sister of the West, forced to exist as long as the Sister did,]] knowing that he failed and he'd never see his friends again.
* The extent of [[spoiler: Paff's miserable existence. She was one of the hundreds rescued from the Shadowlands, and returned home to… no family, no friends, nobody who actually liked or cared about her and a job with a fussy, hard to live with man who constantly compared her to his old assistant. Is it any wonder that she turned to the Shadow Lord? And even then it gets even more depressing, because he withdrew his powers from her at the last moment, leaving her to die alone.]]
* In ''The Towers of Illica'', when Britta collapses in the Blind Tower Sky catches her and apologises to her for not realising that she'd never seen a dead body before. Since Sky isn't shocked or horrified by the sight, it can be assumed that Sky has already seen a lot of death during his childhood near the River Broad. Just how many people did he see starving to death, or dying of illness?