D&D 5E Most deadly monster?

[Sacrosanct]

For the most part, monsters in 5e get a rap for being weak. Certainly true for many when comparing to earlier editions. In TSR era, petrification and poison were largely save or die, and in 5e they are save, then you can try again if you fail. Or keep trying every turn.

But what are some of those monsters that will ruin a PCs day (when compared to when they typically will be encountered by PCs, so not just high CR)?

The intellect devourer? It's a CR2 creature, so mostly encountered by lower level parties if you follow the CR system. But fail an INT saving throw (which many will), and you're truly screwed.

The blue slaad? A CR 7 creature, so mostly encountered between level 6-10 I'm guessing. But if you fail a saving throw, it's a death sentence unless you can find a wish spell. How many level 6-10 PCs have access to a wish spell?

 

[DND_Reborn]

Will-o'-wisps. For a CR2 at-will invisibility and Consume Life are pretty strong IMO. Paired with the right creatures, they can make an encounter go sideways really quickly IME.

 

[rgoodbb]

The Red Mist DM.

But seriously Flame Skulls. Bad day all round. Banshee? Hmm. CR4 Go easy.

 

[CleverNickName]

Banshees are lethal. That wail sounds off and half the party drops to 0hp or flees in terror. Everyone else has to scramble to protect/rescue their fallen comrades from an incorporeal undead monster and her bodyguards. Brutal.

 

[toucanbuzz]

I have to caveat all these with: Or, the PCs get initiative and drop it in 1 round.

• Quickling. This CR1 gave one of my parties fits. With its insane movement, it can run around to your caster, attack a whopping 3x at +8 for a boatload of damage (average 24 if all hits), and flee while being hard to hit at all times. In prior editions, its speed rendered it invisible.
• Intellect Devourer. CR2 that can target a weak save for most characters (INT), and if this doesn't kill you, it might 1-shot you by dropping your INT to 0, and then it might take over the body of your toughest party member. Even if you spot the tiny blindsight bastard, it's got resistance to normal weapons. Nasty.
• Manticore. This CR3 doesn't appear crazy until you have it fly from afar and pepper any ranged PCs with tail spike attacks till they die. Any monster that can fly and (effectively) attack from afar fits this category, such as bow-equipped aarakokra.
• Banshee. CR4, but she can move through walls and fly until she gets where she can take out an entire group with 1 ability, her wail. Not as potent as prior editions, but still any creature that can wipe all PCs with a single ability no matter their current HP is nasty.
• Beholder Zombie. A CR5 that has a 25% chance of rolling disintegrate. Combined with its unwillingness to die and ability to fly, could be nasty.
• Invisible Stalker. CR6 aside, permanent invisibility and strong fly movement means this thing can hit and run, using 3D to hide anywhere it pleases, rendering AOOs and targeted spells useless.
• Solar. It's what I expect from a CR21. A multi-use teleport every round to kite, a sword it can leave anywhere to attack you, and a bow that can instant kill if your HP drops low enough if it's ungodly bonus damage of 6d8 radiant isn't enough. It's one of the few foes that actually might live up to its CR rating against epic PCs.

 

[Oofta]

For a lot of them it's how you run them. Dragons are just a pile of hit points if you fly in, land, and duke it out. Use hit and run tactics, pick up trees to set them on fire and then drop on PCs? Fly behind terrain and wait for your breath weapon to recharge or fly by, snap up a PC in your jaws (assuming the PCs don't have reach weapons) with a grapple and make them your chew toy in private.

But lower level monsters? Flameskulls get my vote. Cast blur, fly in to fireball range. Kind of a one trick pony but at a CR 4, 5 or so are a medium encounter for a level 10 party of 6, right?

 

[Ralif Redhammer]

Intellect Devourer and Mindflayer, easily - you're only, what, two bad rolls from being dead dead deadski.

But perhaps more insidious, are the monsters that can damage your character concept. A ghost can leave a player stuck with a septuagenarian greyhair where they once played a youthful bubbly adventurer.

 

[MatthewJHanson]

For a lot of them it's how you run them. Dragons are just a pile of hit points if you fly in, land, and duke it out. Use hit and run tactics, pick up trees to set them on fire and then drop on PCs? Fly behind terrain and wait for your breath weapon to recharge or fly by, snap up a PC in your jaws (assuming the PCs don't have reach weapons) with a grapple and make them your chew toy in private.

I think young dragons should get special mention, because of the way that breath weapons scale. On average damage a young red dragon (CR 10) can one shot a level 10 character with d6 HD and a +1 Con bonus or a d8 with +0 Con.

Random recharges add to dragon swingyness. A recharge on round two can be brutal.

 

[THEMNGMNT]

I've taken some scalps with the Bodak (CR 6) and Dire Troll (CR 13).

 

[Weiley31]

Tyranny of Dragons' Tiamat.