YMMV / Black Mirror

• Complete Monster: Angelina Gordon, from the second game, is one of the last of the Gordon bloodline. Having been obsessed with the occult since childhood, Angelina intends to free her monstrous ancestor Mordred and legions of demons to overwhelm the Earth. Angelina ritualistically murders multiple people to be sacrifices to the demons, including her long-lost twin brother's adoptive mother. Seducing her twin to manipulate him, with Darren unaware of their blood relation, Angelina guides him to the Gordon ancestral home of Black Mirror where she sacrifices her only ally to test the mansion's traps and attempts to murder her and Darren's birth mother before intending on opening the gates to unleash Hell on Earth.
• That One Puzzle: The first game in the trilogy has a few difficult sliding puzzles that cannot be skipped (unlike in the later games), but the one you find in the crypt in Wales during the third chapter is a doozy. On top of being a tricky 4 x 4 tile sliding puzzle with which you only have one empty tile to work with, just knowing what you need to do requires you to have a deeper knowledge of Western astrology than many people would likely have, specifically knowing the exact order the twelve astrological signs come in a year.