- Take a closer look at Cabal Shadow Priest's artwork. Now compare it with Northshire Cleric's. Did you notice they both have black hair and wear the same clothings? Sure they may not be the same person, but at the very least they are from the same order. And the Cabal Shadow Priest's flavor text makes it all the more chilling.Cabal Shadow Priest: You never know who may be secretly working for the Cabal....
- The boss fight against Vaelastrasz in Blackrock Mountain. He's depicted as being in very real pain because of Nefarian's experiments, and it just gets more and more pronounced as the fight goes on. It gets worse if you play Alexstrasza - you get an Easter Egg, but instead of something funny or cute, he tearfully begs her to save him.
- The trailer for Whispers of the Old Gods. It still has it's moments of whimsy, like the frog with tentacles for a tongue, but it's largely a grim look at what Azeroth is like under the influence of the Old Gods. Made all the creepier by the excellently voice-acted Fortune Teller, who gloats about how hopeless it is to resist their influence, before revealing her true, frightening appearance at the end.
- While some of the things he says are far from creepy, it's still startling when C'thun whispers in your ear after getting buffed and you're not expecting it. Especially if you're wearing headphones, which makes it sound like he's breathing down your neck.
- The Doppelgangster is a 2/2 Dwarf who summons 2 more 2/2 minions as a Battlecry. But considering his very unusual appearance (purple skin) and the minions he summoned are Faceless Ones, it's very likely that the 'Dwarf' is a Faceless himself. Another is the Darkshire Councilman; when you look closer at his shadow, they're very tentacle-y. What's particularly chilling is that Faceless Ones are usually found underground, or close to areas with significant Old Gods' presence. But these 2 cards showed that the Faceless Ones have started to infiltrate local organizations...
- Abominations are very disturbing on their own, especially if you've played WoW and are familiar with their lore. However, Rotface, a Warrior legendary that summons a Legendary every time it survives damage, has a design even more horrific than the other abominations, with his face reduced to a lumpy, fleshy mass with no nose and one eye, and arms, eyes and gaseous pores growing out of his body in almost any place you can name. He also speaks like a Psychopathic Manchild with an extremely agonized voice (as opposed to the typical Abomination's Simpleton Voice). Even worse is that his quote implies you'll be stitched into an abomination like him if you die to him...
- Rotface: Daddynote make toys out of you!
- The end of the Knights of the Frozen Throne campaign. After hundreds of tries, you've finally managed to defeat The Lich King, and your buddy Tirion congratulates you... when suddenly, your hero announces that there must always be a Lich King, as their portrait turns into their Death Knight counterpart and becomes the new Lich King. You're then given a short epilogue showing what your hero does with their newfound power, and it's almost always bad. Special mention goes to Bloodreaver Gul'dan reopening the Dark Portal.
- The Kobold's You No Take Candle is a memetic Running Gag. But come Dungeon Run mode, and you find out exactly why they insist you don't take any candles. In fact, when the relevant card is in play, you will hope you don't take any candle.There's a reason to always keep a light on down here.
- Enjoy using the spellstone cards? Read the poem made by combining the flavor texts of all nine of them in a certain order, and you'll discover some disturbing lore: they were created by Azari the Devourer to tempt mortals into corruption, and most come with nasty side effects: the Amethyst spellstone drew Rin the warlock in a frenzy for power that cost her family and her at the end their lifes, the Onyx spellstones are Artefacts Of Attraction so powerful that adventuring parties turn on each other to have it, the Mithril spellstones protected the dwaves from demons by entombing them alive inside stone golems, the Emerald spellstones turned the tauren hunters that used them into the same beasts they hunted, the Jasper spellstones turned night elves into satyrs, the Sapphire spellstones overwhelmed the shamans who used them with numberless murlocs, and the Diamond spellstones resurrect the dead at a cost unknown to its users...
- The Witchwood's Monster Hunt involves fighting a number of creatures twisted by the influence of Hagatha the Witch, but there are some in particular that are more horrifying than others.
- The Mute, a strange woman with a Mouth Stitched Shut who appropriately speaks in Visible Silence. It's unknown if she's a zombie or a cursed human, but she seems to have some sort of magical power as she is able to silence minions with her cards and Hero Power to reflect her muteness. This ranges from silencing one of your most useful minions and becoming useless, to silencing her minions crippled by a burden such as Ancient Watcher and Humongous Razorleaf, and giving them a chance to beat your hero into a pulp. Her voicelines don't help either, since she mainly speaks in a muffled voice, including muffled screaming upon being defeated and humming an eerie-sounding song when she wins. It's impossible to tell what the Mute is saying through her stitches, but then again, it's probably for the best.
- Inquisitor Hav'nixx looks horrifying, being a Humanoid Abomination with no eyes and skeleton-like teeth, and his artwork depicts him draining two worgens' souls. His introductory description states that he can hear people thinking and feeds on fear. And like that, he is capable of eating souls with his Hero Power, which damages you for half of your health. Most of his lines are creepy, especially his victory quote: "Your soul is... powerful. I will feast for weeks!"
- Crooked Pete has the ability to give his minions Stealth, letting them evade your attacks. Not very scary, right? Wait, WHAT?! He's a Worgen now?! Yes, he's become Beastly Pete and he starts with 50 health and 15 armor, with an aggressive deck to boot. You'll end up having to think on your feet before Beastly Pete clobbers you into submission.
- Experiment 3C is a Frankenstein's Monster-esque hybrid. It is able to eat one of its own minions to draw three cards via its Hero Power, and it possesses the Amalgamate spell to combine every single minion on the field into an Amalgamate just like itself, having all of the tribes in the entire game (shared by its card counterpart Nightmare Amalgam). However, the most disturbing part is its origin: Experiment 3C isn't one of Hagatha's creations, but was created by Dr. Boom. 3C has several lines that show that its components were turned into this monstrosity against their own will; it shows signs of trauma when you play a Spare Part or Unstable Portal as it is reminded of Boom's lab in the Netherstorm, and it does a Freak Out! when seeing Dr. Boom, begging not to be taken back to the lab. Its death quote is "We... finally escaped!" suggesting that Experiment 3C has all of its components' minds and they were aware that they were trapped the entire time! What the hell, Dr. Boom?!
- Gnomenapper, a cursed tauren with an unhealthy obsession with kidnapping live gnomes. Imagine all of the Adult Fear in the gnome villages! To fit his kleptomania, he has a deck full of gnome cards that he presumably stole (even Millhouse Manastorm!) and his Hero Power lets him kidnap one of your minions and put them in a sack, which you must break them out of. His trump card, Sack of Gnomes, lets him fill his board with gnomes, which again, he presumably stole. If you choose Toki, a gnome hero, then Gnomenapper will consider taking her next...
- Toki's final nemesis, her future self Infinite Toki. Toki's time-travelling shenanigans somehow went horribly wrong and resulted in her scarred everywhere including her mind, causing her to descend into madness. After becoming Infinite Toki, she aims to hunt her past counterpart down and Set Right What Once Went Wrong. Her signature cards can be quite scary when you think about it, such as her Hero Power Chronoacceleration, which speeds up a minion so they can attack four times in one turn at the cost of them dying from Rapid Aging at the end of her turn and Alternate Timeline, which completely restarts the match in a different timeline except you will retain your lost health while Infinite Toki fully heals. And even worse, you can't stop her from using Alternate Timeline.
Nightmare Fuel / Hearthstone: Heroes of Warcraft