The most frustrating monsters can sometimes be the most rewarding to defeat – but that’s not the case with these creatures.

These are the most annoying monsters in Dungeons and Dragons. More experienced players might find them boring or overused, and newer players may be unpleasantly surprised by what they can do.

Keep in mind that all monsters can be effectively utilized by a talented DM to make any encounter fun and engaging. In the hands of an inexperienced or sadistic DM, however, you can find your party groaning out loud when you encounter one of these monsters. 

10. Goblins

 I know, goblins are iconic low-level Dungeons and Dragons monsters - but this is precisely why they can be annoying.

A seasoned player can get tired of starting every campaign fighting hordes of goblins until they finally level up and can take on more interesting, challenging enemies. 

Goblins can still be interesting in the hands of the right DM. By setting traps, having them be underlings of a larger, more devious organization, or by role-playing them with humor, you can make these fun for even the most experienced player. 

Goblin/Kobold Details: https://www.dndbeyond.com/monsters/goblin

9. Will-o’-Wisps 

Will-o-wisps can be especially annoying for new players, who have no clue that the lanterns in the distance are actually devious undead luring the party into a trap.

They also have some abilities that are frustrating in and of themselves. Will-o-wisp's have tons of damage resistances and condition immunities and they can turn invisible. 

Will-o-Wisp Details: https://roll20.net/compendium/dnd5e/Will-o'-Wisp#content 

8. Ghouls and Ghasts

These undead creatures are driven by an insatiable hunger that compels them to eternally seek out humanoids to consume. 

Encounters with these monsters can be annoying because of their claw attack, which paralyzes the target if they fail a DC 10 Constitution check. While this is a pretty low DC, the fact that they travel in packs means multiple attacks and a higher likelihood that you will eventually fail the check. 

These monsters are fine when luck is on your side, but if you’re having a night of bad rolling this can turn an encounter into a frustrating ordeal. 

Ghouls and Ghasts Details: https://www.dndbeyond.com/monsters/ghoul 

https://roll20.net/compendium/dnd5e/Ghast#content 

7. Mimics

Mimics are a classic D&D monster. These creatures appear to be ordinary treasure chests, doorways, and other inanimate objects before surprising the party with an attack. 

They definitely can be fun, but the wrong DM can overuse them to the point where players feel like they have to inspect every chest, doorway, and object they come across. 

This gets old quickly and takes up time that could be used on more fun aspects of the game. Like most things, mimics are best when used in moderation and in moments where their impact would be the greatest and most surprising. 

Mimic Details: https://www.dndbeyond.com/monsters/mimic 

6.  Swarms

Rather than one individual monster, swarms are made up of hundreds or thousands of smaller creatures that attack the target simultaneously. There are many different kinds of animals and monsters that can make up a swarm - think bats, insects, rodents, and other small creatures. 

Swarms aren't particularly fun to fight and are more of a nuisance than anything. 

They have resistance to bludgeoning, piercing, and slashing damage and can be hard to deal with at low levels when you have limited access to non-standard weapon damage. They’re also immune to being charmed, frightened, grappled, paralyzed, petrified, prone, restrained, and stunned. 

Swarm Details: https://roll20.net/compendium/dnd5e/Swarm%20of%20Bats#content 

https://roll20.net/compendium/dnd5e/Swarm%20of%20Rats#content

https://roll20.net/compendium/dnd5e/Swarm%20of%20Insects#content 

https://www.aidedd.org/dnd/monstres.php?vo=swarm-of-rot-grubs 

5. Gas Spores

These balloon-like, hollow fungi emerge from rotting corpses. Their malevolent appearance often tricks undiscerning creatures into assuming they’ve just encountered one of the dreaded beholders. 

With only 1 hit point, piercing the shell at all with any weak attack will cause the mushroom to burst and spread deadly spores. Each creature within 20 feet of it must succeed on a DC 15 Constitution saving throw or take 3d6 poison damage and become infected with a disease. 

Spores invade an infected creature's system, killing the creature in a number of hours equal to 1d12 + the creature's Constitution score, unless the disease is removed. 

Even just touching the surface of the fungi can bestow this diseased state on a player. It’s annoying to be surprised into a life or death situation with a strict time limit. 

Gas Spore Details: https://5e.tools/bestiary/gas-spore-mm.html 

4. Invisible Stalkers

It’s pretty much always annoying to fight something you can’t see. As an innately invisible creature, these air elementals don’t become visible when they attack. Your party is essentially waving their weapons around and shooting off spells in random directions, hoping to make contact with the stalker. 

The stalker's invisibility grants it advantage on attack rolls and gives disadvantage to any attack roll against it. It also has resistance to bludgeoning, piercing, and slashing damage from nonmagical weapons and tons of condition immunities. 

Invisible Stalker Details: https://roll20.net/compendium/dnd5e/Invisible%20Stalker#content 

3. Rust Monsters

Rust monsters scurry through subterranean tunnels and the caves of the Underdark, seeking out metal. 

With the ability to degrade or destroy any metal object within five feet of it, these monsters can be a player's worst nightmare. Imagine spending a decent amount of coin on a new suit of armor or hunting down a rare weapon, only to have it degraded or deteriorated by one of these devious little creatures.

While only nonmagical weapons can be destroyed in this manner, this can be devastating to a group of lower-level adventures with limited access to magical equipment. ,

Rust Monster Details: https://www.dndbeyond.com/monsters/rust-monster 

2. Black Pudding

These dark, sticky oozes lurk in dim passageways, appearing as nothing but a shadow.

 Like the rust monsters, black puddings can degrade a player’s weapons and armor. Any flesh, wood, metal, or bone dissolves when it comes into contact with the goo.

They also have tons of immunities and resistances. Any lightning or slashing damage inflicted on the pudding splits it in two. One annoying enemy can easily turn into two or three or four.

Black Pudding Details: https://www.dndbeyond.com/monsters/black-pudding 

1. Gelatinous Cube

Gelatinous cubes are transparent oozes that scour dungeon passages, picking up whatever objects or creatures are in their path. 

Even when in plain sight, it takes a successful DC15 Wisdom (Perception) check to spot one that hasn't moved or attacked yet. They’re guaranteed to almost always surprise at least one member of your party. 

Gelatinous cubes can also consume party members, taking them out of the fight completely. Engulfed creatures can’t breathe, are restrained, and take 6d6 acid damage at the start of each of the cubes' turns. 

While challenging, these monsters aren't’ particularly fun to fight. Gelatinous cubes aren't intelligent, can’t communicate, and often aren't part of a larger story. Really, they’re just a pain to deal with. 

Gelatinous Cube Details: https://www.dndbeyond.com/monsters/gelatinous-cube 

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