SEVENS is easily the most light-hearted and wacky entry in the franchise, but it's still Yu-Gi-Oh!, and still has its moments of terror.
- The first Maximum Summon is an in-universe case of this for the heroes, with Yggdrago the Sky Emperor being the first utterly massive monster seen in the series and defeating Yuga in an instant. The low lighting that keeps the monster in shadows aside from brief flashes of lightning and its very alien appearance only lend to this.
- The President Drone. When Mimi puts it on, her body is shocked by electricity and falls limp, before it takes partial control of her. It later proves capable of a Villain Override on Mimi when dueling. Oh, and that chuckling noise it makes? That's its way of keeping its host silent.
- Neiru's backstory. When he was three years old, he hacked into Goha's satellite network and destroyed a good chunk of them causing them to rain down on the city. It was a good thing that the debris didn't hurt anyone and his parents got him into Duel Monsters. Had Neiru had continued to be left to his own devices, he could've become a much scarier threat than he was in the Maximum arc.
- Sebastian's Dwell Chair deck. Given that it's a Dark themed deck, it has to be some level of creepy. And even though the episode itself was on the sillier side, Sebastian summoning Throne of Darkness was offputting. And it's even more disturbing watching it move in motion due to the CGI effects!
- On a similar note, Sebastian’s Villainous Breakdown, wherein he utterly loses his cool after Yuga gets past his One-Turn Kill and instead becomes completely enraged, acting borderline sadistic at points. His face glitching out really doesn’t help.
- And at the end, when Yuga defeats him, he just breaks entirely and kneels on the ground, numbly reciting a Madness Mantra. The kids are understandably freaked out and are then lifted out, leaving him alone in the darkness.
- The beginning of Season 2 where Yuga's dream involves a destroyed Goha City with him and his friends about to challenge a meteor falling on the city. While there's a Hope Spot with Yuga and friends showing unyielding courage by blocking the meteor with the power of Rush Duels, it's quite shocking to see such a tonal shift compared to Season 1's opening with Yuga piloting a giant Dueling robot.
- Episode 58 gives us the most unsettling episode in the series by far. Yuo arrives with his mechanical puppets in a fashion that may remind you of Yami Bakura from the original DM. His voice and mannerisms are just plain creepy to listen to, and he's the first duelist in the series to claim to enjoy his opponent's suffering. We also have a scene were Luke encounters a puppet Yuga in the school hallway where the lighting is red like a horror movie.
- To top all of that, we get the return of Fusion Summoning, which is handled in a completely different way that we're used to seeing. Compared to the original series where Fusion was the merging of two regular monsters, SEVENS frames Yuo's Fusions as the forbidden merging of two monster types to create a new type which makes this summoning method feel like more of an abomination more than anything.
- Yuo's ace monster: Metallion Asurastar. The thing looks very unsettling to see in both action and appearance; it's best described as all the worst parts of IV's Gimmick Puppets from Yu-Gi-Oh! ZEXAL and Sora's Frightfurs/Des-Toys from Yu-Gi-Oh! ARC-V, and it's constantly twitching in an uncanny manner. Special note goes to the way that it destroys Yuga's Vast Vulcan by piercing into its chest and spinning around to rip it apart inside out, all while laughing creepily.
- The finale where Yuo quietly whispers "Fusion..." to taunt Yuga and friends as they're slowly being surrounded by puppets in his circus as the episode ends.
- Yuo's reaction to Yuga being excited about Fusion instead of frustrated and despaired? Why, to attempt to ensnare Yuga and his friends in an Iron Maiden, blast them off of Sixcross, and suffocate them in the vacuum of space. If Tiger had not been there to rescue them, Yuga and his friends really might have been trapped and asphyxiated.
- While Yuo's Metallion Vritrastar mercifully isn't nearly as nightmarish as Metallion Asurastar, the shriek it makes when Yuo powers it up is quite unsettling.
- The President Drone is not the only one of its kind, as the multiple Drone helmets can also control people. Among these are The☆Lukeman, and it's hinted that Nanaho's hat is another.
- Episode 74, the Zombie Apocalypse turning the episode into a Zombie Horror Movie, even if there is no blood.
- Episode 76-77, Guruguru becomes a zombie and end up acting like some feral animal, which was caused by Nanaho showing a Forbidden Card to Guruguru. Turns out that Guruguru was actually the 6th Goha Sibling known as Yuga Goha, and he was revived by the use of the Monster Reborn card in his duel with Yuo. It's even more frightening that Guruguru goes from a cute kid in a chameleon costume to an Eldritch Horror that turns into an evil version of Yuga and that the costume is now just a husk, which devastates Luke considering he was Guruguru's best friend.
- Episode 91, Otes' Fusion Monster, Magician of Dark Sevens, is a callback to Yami Marik summoning and fusing with the Winged Dragon of Ra, but this time it's Otes' corrupted Sevens Road Magician combined with a creepy dark demonic dragon and serves as the Final Boss of Yu-Gi-Oh! Sevens.
