What monster or type of enemy gives you or your party the most trouble?

[MarkVIIIMarc]

For my Bard, demons and devils with their advantage on spell saves are tons of trouble. Ever since we've moved on to fighting humans and things I can frighten en masse it has been great.

What trips up you all?

[Blood of Gaea]

A Lich riding a Tarrasque. Yes, that happened. No, we didn't win.

[Nod_Hero]

Stuff that paralyzes or poisons or both is a common theme lately in one of my campaigns.
The DM has thrown us for a loop so much that we're unattuning from more powerful items to pick up a Ring of Free Action and similar magic gear.

[strangebloke]

AOE or getting separated from the party. If you're expecting the first, you spread out. If you're expecting the second, you bunch up.

If you guess wrong?

Heh.

One of the perils of custom monsters.

[Wisefool]

Do doors count?

[Afrodactyl]

As a DM? I'm a huge fan of using ghouls against my party, at various levels. Once one player succumbs to the paralysis it all goes to pot and the rest of the group starts panicking.

Personally? Despite writing up lots of martial characters, I generally use casters when actually playing, so anything resistant to magic or status effects just shuts me down. We recently had a run in with a paper Golem (homebrew) in a magical library, and that thing resisted magic, and stored spells it was hit with. I was mortified when it sent a fireball of its own back at us after taking one to the chin.

[Chugger]

Nothing at all. After Xanathar power-creep we hit so hard and cheese darkness and stuff - we just kill everything. It's a problem.

[Kane0]

Do doors count?

That sounds like there's a story behind it.

[DarthPenance]

Do doors count?

Doors, truly the most powerful enemy of DnD, and I'm not talking about mimics.

Well, for me I guess devil/demons, since they're resistant to non-magical weapons, immune to fire and have advantage on magical effects, really we only get effective against them thanks to our paladin.

[Kane0]

Doors, truly the most powerful enemy of DnD, and I'm not talking about mimics.

And of course their greater counterparts, the dreaded Gazebo

[Unoriginal]

Nothing at all. After Xanathar power-creep we hit so hard and cheese darkness and stuff - we just kill everything. It's a problem.

What kind of power creep is supposed to have happened to make you in invincible ?

[JackPhoenix]

Humanoids. Intelligent foes who use the same tactics they do, often come in groups which mix melee prowess, ranged combat and spellcasting, and can be pain in the butt even outside direct battles. They even use other creature types (like trained animals and other monsters, undead or constructs, summoned outsiders, etc.) to fight for them!

As for most trouble... I remember this indestructible zombie. No matter how long and hard were they hitting it, it just wouldn't stay dead. It was a simple zombie and no big threat on its own, but they didn't have a source of radiant damage (paladin wouldn't waste smite on a zombie, though she seriously considered it by the end of the combat) and the rolls on Undead Fortitude were just crazy. I don't think I've seen 3 nat 20 in a row before or after.

From time to time, they've noticed a small, gnome-shaped zombie staring at them. No small feat, considering it lacked a head. It looked familiar.

[Sception]

Mind flayers with pet intellect devourers.

[ToastyTobasco]

Intellect devourers.

Our party is kinda dumb, and full of newbies