It's not an Atlus game unless it's ridiculously tough, has addictive music, and fills you with absolute dread every time you step into a dungeon.
- Some enemy designs will qualify, from the one-eyed worms to the giant, man-eating plants with far too many teeth.
- This series in general has FOEs (Field-On Enemies), roaming enemies that not only are far stronger than regular enemies, but also appear on-screen. While this wasn't so bad in the DS games, all games after Etrian Odyssey IV began showing the monster themselves in the field. Oh, and don't think that jumping into a battle with a regular random encounter will save you; FOEs will continue to move about the map as you fight, and if you're not paying attention to your map (which continues to be displayed in battle, by the way; this is why), the FOE will show up alongside whatever you're currently fighting and start attacking you. This can lead to a few tense moments, such as a Jungle Killer appearing out of nowhere when you step on a certain tile or that rock just ahead of you suddenly coming to life and revealing itself to be a Boulder Boar...
- And that's not even taking into account the BING of an FOE noticing you and deciding to hunt you down. What makes it worse is that, in some of the games, the FOE's marker on the mini-map turns crimson when it starts the chase. In other cases, that "BING!" is your only warning of an FOE's presence.
- If the FOE steps into your space in the middle of a battle, the screen will flash abruptly and the FOE will let out a roar. And of course the standard battle theme changes to the much more urgent FOE fight theme as you realize that your unawareness of your surroundings or just plain bad luck has led you to the death of yourself and your friends.
- There's nothing more pleasant than opening a door and immediately hearing the FOE chord. Whether the FOE is right in front of you or not.
- In the roguelike spinoff Etrian Mystery Dungeon, the D.O.E.s are not only powerful enemies visible on the map, they can travel between floors just like your party. Running away to the stairs? No escape, boyo, they'll follow you right up! There are other attributes they possess that make them even more terrifying:
- They will take very little damage per hit until you hit them with status ailments and binds. A desperate player might frantically spam the wrong status spells or binds ineffectually until it's too late.
- They often possess a special ability that acts like the Monster version of the Recall Scroll, warping in monsters from all over the floor to dogpile you.
- As large 3x3 enemies (an attribute inherited from certain on-map bosses and extra-large F.O.E.s from the mainline games), they will demolish narrow tunnels and turn them into 3-space hallways as they pursue you.
- Let them reach the surface? They will attack the town and damage the infrastructure so bad that even after rebuilding it will cost you all the upgrades you've invested in any property they destroy. And you thought regular monsters escaping to attack High Lagaard in The Knight of Fafnir was bad news.
- The games pull no punches when describing dangerous or horrible events; detailing the carnage caused by the beasts, or the spine-chilling feeling of sensing a dangerous FOE nearby. The level of detail put into the descriptions is so deeeep that you'll be left either terrified or squicked out at the thought of what it would be like if you actually saw it.
- The three "terrible stuff is happening themes" that often accompany these events — "Red and Black" from I and II, "Unknown Menace" from III and V, "Imminent Calamity" from IV, and all of them in Nexus — are all designed to make the player crap their pants.
- A meta example exists in fanart - as said above the games in general do not shy away from detailing the gory fates of failed adventurers, and there are a number of fanartists who do not back down from that. If you go trawling for fanart, don't be surprised to find art depicting Total Party Kills and the adorable characters mauled in various ways. And it's not even Gorn or anything, because it's just matching the descriptions you can read quoted below.
- Any time a battle theme is preceded by a Sting and a red leaves transition (indicating an enemy ambush), you know you are about to see your party likely get ripped apart, with some grayed out 0-HP status boxes or even the Game Over screen if you're unlucky.
- If you see the phrase "(enemy) stands ready!", you know that if either it or its partner aren't taken care of quickly, your party is going to get totaled.
- The two words you never want to see when on a gathering point (followed by an enemy ambush, and, if your team is farming-optimized, a likely Game Over):
Etrian Odyssey I/Etrian Odyssey Untold: The Millennium Girl
- Red and Black, the song you don't want to hear in the dark at night.
- In the Azure Woodlands, there are a number of FOEs waiting in the water on some floors. While in the original they are invisible, Untold shows them as being there. And unlike others, they won't attack. They simply wait. Staring at you. Waiting for you to get into a battle nearby them...
- The fifth stratum is the ruins of Tokyo, which hits you like a ton of bricks. Seeing a modern-day city reduced to abandoned ruins is quite tragic.
- The Claret Hollows of the original Etrian Odyssey. When you find the hidden stairway down in the room where you fought the Final Boss, your first response is to get excited for the opportunity to explore more. As you go down, you get this sight◊ on your screens. The walls are made of flesh and bones, the doorways look like heart valves, damage tiles are stomach acid, and the True Final Boss is titled "the Heart of the Labyrinth". Did we mention the whole stratum is covered in blood and is very claustrophobic compared to the others you've seen so far?
- If you had any doubts about the floor before, The Millennium Girl's version brings back the footstep sounds from the Bonus Dungeon of the last stratum in the fourth game. Which, as mentioned below, sounds like you're stepping in blood.
- To make matters worse, some floors feature the strongest FOEs in the game, the Macabre/Depth Dancer, which spawns infinitely and has a chance to summon instant death enemies. And they love to ambush you from behind when you least expect it.
- Primevil from the first game, as mentioned before, has a very Lovecraftian appearance.
- It's bad enough to be Yggdrasil's Core, but one of its attacks is called Necrosis. If you know about the actual medical condition, or looked it up, it becomes much worse.
- M.I.K.E. mentions that out of the seven Yggdrasils, only two were fitted with Gungnir units (Etria's and Gotham's). Etria's was stopped in this game and the Yggdrasil Core destroyed. Gotham's Gungnir was successfully fired and its Yggdrasil destroyed. High Lagaard's Yggdrasil was hijacked by a lunatic attempting to create immortal humans, and has its own core mutated and sealed by demi-humans for centuries. Armoroad's* has trapped an alien entity underneath itself and started converting humans into Yggdroids to fight it. Tharsis' was broken into pieces until the Empire's disastrous attempt to control it, which spawned the Heavenbringer. And yet there are still two Yggdrasils out there, and who knows how they are faring...
- The Gungnir units themselves. There's a cutscene in which Ricky asks M.I.K.E. to show the projected devastation its activation would bring. The screen is covered in enormous swathes of destruction, with all population centers flashing a "NO SURVIVORS" warning.
- Hell, the fact humanity had to go and trust in the Yggdrasils to survive, knowing full well just how dangerous they could become. Worse, their failsafes (Gungnir, the Warped Savior) were just as dangerous or worse than the damn trees.
- M.I.K.E. falling prey to A.I. Is a Crapshoot and trying to activate Gungnir, not caring that, one, an incompletely charged Gungnir won't even scratch the Yggdrasil Core, two, Gladsheim is within the blast radius, or three, Etria and an enormous surrounding area will be pointlessly vaporized into oblivion.
Etrian Odyssey II: Heroes of Lagaard/Etrian Odyssey II Untold: Knight of Fafnir
- Think you can just gather a bunch of material and sell them for a profit like in the first game? Prepare to get very well acquainted with sudden ambushes by monsters far more powerful than you, something the original game never so much as warns you about. No doubt many a gamer watched in horror the first time a Rafflesia wiped their gathering party.
- The mission to find the missing soldiers in the Ancient Forest. You take the job, heading into an area that a member of another guild thought to close off to protect others from. And what do you find?
- It gets worse. The monster who did this? It's an FOE far stronger than your party. And it's still there.
- This is extra goodtime fun in Fafnir, because now your party members can talk and react. Poor, innocent Arianna, who'd previously been upbeat about the whole adventure, pretty much looks like she'll never manage to sleep again through the whole thing and can barely manage to say anything. Even your buddy Flavio is shook down to his very core. And yes, it's clear the scene is just as horrific in this version as the original.
- The remake of the game begins to play with visual expectations of the player. An FOE can be anywhere and everywhere. That treasure chest? It's a Mimic in disguise, waiting to devour you whole if you drop your guard. That empty patch of flowers? A Petaloid is hiding in it. Stepped a little too close to a seemingly empty corner? You've not only alerted an invisible FOE, but also about three others that were also hiding in the same room.
- The worst offender comes in Ginnungagap B3. Usually, an FOE makes itself known in some way or form, whether having visual cues or the party pointing it out on the map when encountering it for the first time. But here, you get nothing. Just the sound of the "FOE has noticed you" noise and an empty corridor. And then, as you take your eyes off of that wall just ahead, you realize it's not empty far too late...
- One of the postgame superbosses announces itself to the world by attacking High Lagaard directly. While no named character or key building is damaged by the attack, this event terrifies Cass so much he'll hide under his bar until you best it.
Etrian Odyssey III: The Drowned City
- In the Undersea Grotto of The Drowned City, there's a cutscene where you're tricked into being cornered by three FOEs, with the third game's version of Black and Red playing in the background.
- Worse yet, there's an event with the Murotsumi Guild in the very same Stratum, with Agata trying to head to that location while Hypatia tries to warn him against it due to a premonition. Whether you tell him where to go or encourage him not to head there, one of them will be violently killed by those FOEs.
- The 6th Stratum of this game might just be the most nauseous of the series : It's a Tentacle Forest with eyes EVERYWHERE! If future games ever want to play the "Nausea Card" further, they're gonna have to do something either so gross it risks raising up the rating up to M or incredibly eldritch to top this freaky place.
Etrian Odyssey IV: Legends of the Titan
Etrian Odyssey V: Beyond the Myth
- This game's awesome arrangement of "The End of Raging Waves" starts with a very intimidating choir chant. It's used as the music for those massive 3x3 FOEs that you see starting in the second stratum in place of the usual FOE theme, basically meaning that unless you're at endgame levels, you really need to run away right now.
- Look closely at the Eerie Chokers in the third stratum. They don't have claws like the Ropers that they resemble, they have human hands.
- The third stratum, the Fetid Necropolis. The entire place is fairly dark (you can still see, but the place is notably muted in lighting, even during the day) and littered with bones and graves, several field events involve spooking out your party members (for example, you find an oddly-cold spot and when you try to examine it, a slug falls onto the person checking and they proceed to have a Freak Out), and some of the FOEs include undead skeletons that suddenly pop out if you approach their resting spots (indicated by a seemingly-innocent arrangement of bones) and wraiths that can go through walls. Oh, and said wraiths go off the radar whenever they're in walls, meaning that it's possible to be blindsided by one of them if you're walking next to a wall.
- The description of the scene around Dryad is pretty gnarly - it is immediately clear that she uses her pretty looks to lure people in so that she can murder them, and she delights in the expressions of horror your party no doubt has when they realize that Jenetta's "new Friend" has a really nasty hobby.
- The first time one encounters a Mounting Horror — the first FOE in the sixth stratum — it's distant enough that one can barely see its silhouette, and it looks hideous enough to dissuade the player from approaching. Then they take a step, and it demonstrates its unique gimmick: it duplicates itself, and that one can pursue.
- Speaking of the 6th Stratum, once you and Arken reach the final floor, things get intense. She quickly finds out that her ENTIRE FLEET AND HOMEWORLD was eradicated by a god-like being known as the Star Devourer.
- Should you pass the 6th's Stratum's final door as normal, you are greeted with the credits. Nothing special. However, should you release the two seals on the 30th floor and then enter the final door...
Etrian Odyssey Nexus
- So you've ventured to the bottom of the Lush Woodlands and taken out the Berserker King. Great work, time to go back to town—hoo boy, did "Imminent Calamnity" just start playing again? Yep, and where the Berserker King once stood is Cernunnos, who has cornered your party and prevented you from escaping, even via Ariadne Thread! Fortunately, Wiglaf comes in to give your party a full heal, and you can save your game, but it still doesn't change that you have to fight this new boss with no way to reorganize your party and restock. The game also gives you a unique and stern warning when saving to save to a new file and that the game could be "greatly affected" (read: Unwinnable by Design) if you save over an existing file, especially if it's your only file.
- The backstory and description given for how the Scarlet Evil Eye works. A man searching for a way to save his terminally ill daughter eventually finds a way to replicate a vampiric curse and develops at least two contact lenses to inflict it. One was with his daughter until she took it out to kill herself after his own death, the other buried in the Southern Shrine with memos detailing the research and the process. The lenses devour the person cell by cell, replacing each one with vampiric copies, until the entire body has been replaced. Your guild at least has warning as to what is involved so they can weigh the risks, but anyone who somehow finds the other lens won't be so lucky.
- In the Western Shrine, you can find boulders that block the hallways and need to be pushed around. The first time you find one, nothing bad happens...because you can only push it twice before it's backed into a dead-end. The second time you see one of these boulders, however, you push it a third time, the FOE warning beep plays, and the rock turns out to be a large pillbug FOE in disguise, who's now cranky from having its slumber disrupted!
- Partway through the game, you notice that Princess Persephone has started to fall ill, forcing Muller to take her post in the Expedition headquarters. Eventually she straight up disappears. When you reach the 11th Labyrinth, you and Enrica discover why: Blót has kidnapped her and brainwashed her with his Hexer skills (and if you've never played the first two games, since Hexers aren't playable in this game: Yes, mind control is part of their skillset), and if you look closely at her portrait, her eyes are blank to reflect this. It's then and there that you see that everyone was right to suspect Blót feeding info both to Maginians and Seafarers.