Pre-published, official campaigns for Dungeons & Dragons Fifth Edition supposedly contain some level of balance to stop them from being cakewalks or slaughters. However, sometimes these good intentions don't pan out. Even in company-approved adventures, sometimes the odds are stacked against the heroes.
This comes out of a tradition that dates back to Advanced Dungeons & Dragons' earliest adventures, from the infamous Tomb of Horrors to the life-destroying Soul Gem in The Ghost Tower of Inverness. However, this doesn't make these encounters any more enjoyable for players. Whether they're outgunned, outnumbered, or set in a deadly environment, some D&D encounters are famous for their difficulty.
Updated 21st of December by Isaac Williams: Ideally, encounters in D&D campaigns are dangerous but not overwhelming. However, there is no shortage of unbalanced fights in Fifth Edition's many premade campaigns. This list has been updated with even more of D&D 5e's most dangerous fights.
10 The Old Bonegrinder Massacres Low-Level Characters
Curse Of Strahd
Curse of Strahd is one of 5e's hardest campaigns by design. It takes place in the dark, horror-themed setting of Ravenloft and casts the players as underdogs against the powerful Strahd. Death lurks around every corner. The windmill Bonegrinder, inhabited by a coven of Night Hags, is one of the deadliest spots in the entire realm.
A trio of Night Hags, with the powerful boosts they get when they fight together, is a challenging fight for many parties. The Bonegrinder is made more egregious, however, because the PCs are expected to come across it at level 3 or 4. Even facing the Bonegrinder several levels higher can be challenging. At low levels, it's a near-guaranteed massacre.
9 A Trio Of Assassins Are Dangerous Because Of An Error
Hoard Of The Dragon Queen
It's rare, but skewed balance in an official encounter can stem from a genuine mistake that later has to be corrected. The most notorious of these is Hoard of the Dragon Queen. In that campaign, a low-level party can come across an inn taken over by a trio of assassins who they may well have to fight.
When the encounter was planned, the assassin was a much weaker CR 3 enemy. Before the book's release, however, the stat block received a significant buff. Assassins became CR 8 with a host of offensive abilities. For a long time, the book was not updated to match the intended party level. The result is an extremely unbalanced encounter.
8 Saltmarsh's Smugglers Put Up A Surprising Defense
Ghosts Of Saltmarsh
The Sinister Secret of Saltmarsh adventure takes place in a supposedly haunted house. After fighting a few vermin, the party learns that the house is in fact the hideout of a smuggling gang. If the PCs make the wrong move, they can put the entire gang on the defensive.
The gang includes three hobgoblins, several scouts and bandits, and a spellcaster. Even if the party fights them piecemeal, it's a tough series of encounters. It gets much harder if the gang presents a unified front against the party. However, it is explicitly a consequence of the party tripping the smugglers' traps or getting detected.
7 A Surprise Manticore Attacks During A Mundane Mission
Dragon Of Icespire Peak
Dragon of Icespire Peak is explicitly designed as a campaign for newcomers and is included in 5e's starter set. One of its first adventures seems simple and safe. The PCs travel to the home of a woman who lives outside the town of Phandalin and encourage her to join the town for safety.
There, they encounter a Manticore. This is a CR3 creature that can fly and attack from range. Its attacks deal more damage than level 1 characters can take. The intention seems to be for the players to realize that they are outmatched and try to find a peaceful solution, bu D&D newcomers to recognize the threat and take this option.
6 Baba Lysaga Attacks Alongside Her Hut
Curse Of Strahd
Nearly every inch of Curse of Strahd's Barovia has something deadly lurking in it. Few spots, however, are deadlier than the ruined town of Berez. Baba Lysaga, who lives in its center, isn't always a mandatory fight. Nonetheless, there is a good chance the players will need to go to Berez to retrieve an artifact.
Baba Lysaga is no minor threat herself. She is a witch who can fly while casting several brutal spells at the party. However, she is also backed up by her animated hut. This is a monstrous hulk of a creature with several vicious attacks and over two hundred hit points. The two cover each other's weaknesses and present a huge threat. Most parties can't survive a drawn-out fight against both of them.
5 Flennis The Necromancer Plays With Fire
Baldur's Gate: Descent Into Avernus
Baldur's Gate: Descent Into Avernus is controversial among 5e's published modules. Some question its quality and particularly its early-game balance. One adventure the players tackle at second level is the Dungeon of the Dead Three. This dungeon is piled high with threatening encounters.
However, the most notorious part of the Dungeon is the fight against Flennis. She's a necromancer with a surprising trick up her sleeve in the form of Fireball. This third-level spell can easily down or even kill an entire party at that low a level. Common advice for running the adventure is to have Flennis cast other spells instead, as even a single Fireball could lead to a Total Party Kill.
4 *The Goblin Ambush Can Overwhelm A Low-Level Party
Lost Mine Of Phandelver
One of the first D&D encounters many players will face can be a brutal one. Lost Mine of Phandelver, in the original starter set, starts with an ambush. Four goblins attack the player characters' convoy. Ordinarily, this sort of fight wouldn't be a real danger. However, these goblins start off hiding.
The goblins have a +6 to their Stealth modifier. This makes them capable of surprising most characters and getting a whole round of free attacks against the party. At first level, a single attack can knock a character unconscious. With surprise and the fragility of low-level characters, four goblins can easily defeat a party of first-time players.
3 Acererak The Lich Is Practically Death Incarnate
Tomb Of Annihilation
Tomb of Annihilation is another module designed from the ground up to be a challenge. It's a difficult crawl across a hostile environment with several brutal and trap-filled dungeons along the way. The final battle against its villain, Acererak the Lich, follows suit. He is one of the most dangerous enemies printed in an official adventure.
Acerak's spellcasting capabilities are a major problem. He has access to Power Word Kill and the ability to cast it three times, potentially picking off half the party immediately. Furthermore, he appears after several other challenging boss fights. These include battles against an atropal and against the Soul Monger itself. The party's best hope is to receive massive buffs from the Nine Gods before fighting him.
2 The Coffin-Maker's Shop Is An Unforgettable Ambush
Curse Of Strahd
The town of Vallaki initially appears to be something of a safe haven for the PCs in Curse of Strahd. It's free of the vampire lord's influence, but it contains one of the most infamous encounters in the module. On a quest to return the bones of a saint to a church, the party has to enter a coffin-maker's shop. Inside, they are ambushed by a group of six vampire spawn.
A smaller number of spawn would be a dangerous encounter. Six together are all but impossible to kill before they overwhelm the PCs. The PCs can try to retrieve the bones and flee. However, the spawns' speed, grappling, and high damage make even that a risky prospect. This encounter lives on in infamy for its challenge and its unexpected nature.
1 The Blue Dragon Occupying Greencrest
Hoard Of The Dragon Queen
Dragons are a major threat in D&D. Even the youngest categories present considerable challenges to low-level parties. Despite this, the party can come up against Lennithon, an adult blue dragon, on their very first day of adventuring in Hoard of the Dragon Queen.
The party isn't expected to kill Lennithon. They can simply drive her off by doing 25 points of damage. But even that is an incredibly risky proposition for a group of first level characters, particularly after the other challenging encounters the party face throughout Greencrest. There is a good chance at least one party member will die to Lennithon's lightning breath before they can.