- The first episode ends with Leo and friends saving the day and stopping Quetzalcoatl's summoning... but then the whole town is swallowed up by Quetzalcoatl's darkness, along with all its inhabitants minus Leo and his friends. Just the fact it happens so suddenly after Leo kissed Marcella makes it all the more terrifying to see.
- Just about every Monster of the Week counts thanks to their terrifying appearances and threat levels. Here's a list of notable examples.
- The Jersey Devil. It was born a normal child but as it grew, it became more and more monstrous until it became a demonic creature.
- The Nicht Mart. We're introduced to this supernatural monstrosity when Leo lays down to sleep after the crew found themselves in a town inhabited by sleep-deprived people. Leo soon finds out why they're so sleep-deprived when the Nicht Mart stabs its fingers into his head and forces him to dream horrible nightmares. The only way to fight back against it is to not be afraid of it, causing it to flee to another town. Thanks to Don Andres actions during his life, however, the Nicht Mart refuses to leave the town it settled in and continues feeding on their fear every night for generations until its defeated.
- Fenrir. In his own words, I can eat anything. Imagine if Leo and the gang were YOU.
- Oh sweet lord, MISTER MADERA! It's a Tsukumogami, an inanimate object that comes to life on its hundredth birthday, that feeds on the souls of the living and dead, turning them into dolls afterwards. It turned all of Leo's friends into dolls and very nearly turned Leo into one too. Even without the soul sucking powers, Mister Maderas is terrifyingly fast and smart. It makes sure to dismantle the ship, with an ax no less, just to make it easier to steal its prey's souls.
- While it is thankfully undone soon after Marcella's death can be pretty shocking especially since she Dies Wide Open.
- Teodora hearing the sounds of the heart monitor hooked up to her comatose body while the link her astral form has with her body is weakening. It's as if she's hearing the grim reaper's footsteps and treats it like anyone else would in her situation. With absolute body-freezing terror.
Nightmare Fuel / Legend Quest