Creepy Child: Jane Penvellyn.. There's just something so damn creepy about her... which proves to be not that far off when she turns out to be the culprit.
Genre Savvy: Randulf the Red, so very much. Instead of hiding his treasure behind just one puzzle, he arranged a Thanatos Gambit in which every branch of his family added a puzzle on top of his own, ensuring that said treasure's protection only got stronger and stronger as the generations progressed. The only reason anyone outside the Blackmoor family could find it was because of the malice of Jane, the latest Blackmoor heir, whose crimes threw a Spanner in the Works — that is, Nancy.
Improbable Infant Survival: At the end, Jane, the preteen culprit, accidentally gets stuck in a potentially life-threatening trap which you must free her from... except no matter how long you take, she never dies, despite being stuck in an enclosed space that would guarantee suffocation within minutes. Strangely enough, if you don't move out of the way of the trap in time, you get stuck in there with Jane - and you get a Game Over.
Induced Hypochondria: Linda is a victim of this in Blackmoor Manor, being led to believe that she's been cursed and is turning into a werewolf. It turns out to actually be caused by her stepdaughter slipping hair growth treatments into her lotion. Lampshaded in your phone conversation with Paliki, where the placebo effect is discussed at length.
Legacy of Service: Ethel comes from a family who has served the Penvellyns since at least the Middle Ages. Not only does she teach Jane astronomy, math, science, French, and other varied subjects, she also serves as Jane's introduction into the long-standing and confusing traditions of the Penvellyn family. And she's completely necessary for this, because the traditions are passed from grandchild to grandchild, thus making it very difficult for the Penvellyns themselves to pass on the knowledge.
Maybe Magic, Maybe Mundane: The Penvellyn family's great success and wealth is attributed to a meteorite piece that Randulf the Red, originator of the line, discovered and believed to be the legendary Philosopher's Stone. Whether or not the meteor actually has magical powers or is simply a good luck charm is never confirmed.
Nothing Is Scarier: The secret passages invoke this — dark, dank tunnels with ambient background music that sounds like dripping water. The only light source is a green glowstick that illuminates a small patch of the hallway at a time, leaving everything else pitch black. Even if you just checked the shadows, and you know there’s nothing there... you’ll wonder.
You never actually see what is happening to Linda... only given two very big tantalizing hints...
Only Smart People May Pass: This is the whole point of the puzzles created by each Penvellyn grandchild to protect the Philosopher's Stone. Randulf the Red, the first member of the clan, wanted to ensure that his descendants were clever and wise, so he insisted that each successive grandchild both create a puzzle to guard the Stone and solve all the puzzles by their predecessors to find the rock's hiding place.
Technology Marches On: An In-Universe example occurs with the Penvellyn family's puzzles to protect their legendary treasure, a large meteorite which they believed to be the Philosopher's Stone. Each Penvellyn grandchild is tasked with developing the latest challenge, and it's possible to use those challenges to trace the evolution of technology from the Middle Ages to the present day. For example, the original puzzle is a set of moving rooms; one toward the middle of the chain involves an automated game machine with an antique robot; and the latest, from Jane's grandfather, involves finding a series of hidden ghosts to get the password for a locked file on his computer.
