The most fearsome, frightening monster in any RPG is...

[Jack Of Owls]

You know, except for maybe Dark Souls, I almost never feel any real tension playing any modern or olden' days RPG. I mean, it's just a game, right? You fight, you die, you reload, you fight again, you die again, you run away to fight and die and reload another day. But if you're not a save scummer, there is one critter in the D&D universe that sets me a'tremblin' at the mere sight of it. The ultimate griefers - rust monsters. Oh, no! My beautiful adamantium armor! My jewelry! My rings! My amulet! My gloves! My goodness! I'd rather face 20 beholder mages, 10 medusas and a basilisk in a pear tree than ONE rust monster. What do you fear most in an RPG?

 

[Parsifarka]

 

[an Administrator]

Walton Simons

 

[Joni Odin von Hassenstein]

 

[Quigs]

Plague Sharks in old EverQuest. To go between some zones you'd have to sit on a boat as it traveled the oceans that were full of creatures waiting to kill you. There were no in game maps or compasses, so in the open ocean, you were pretty much going to get lost and die if you fell off the boat. Being a game built upon the old school mentality of not giving a fuck about 'safe zones', the oceans had sharks that were going to be about 5-10 levels higher than you, and plague sharks, that were going to be 25+ levels higher than you. Unfortunately, once and a while, the ship would sail straight into a shark, which bugged the game out so that it was now on deck, eating people.

Travelling was fucking dangerous.

 

[Mustawd]

The Butcher in Diablo 1 was scary.

Also, I remember in Avernum, there was an enchanted book that if you read from it, like 4 demons would spawn and decimate your party.

Both were, "oh shit!" moments, but the first was actually scary. Then again I was pretty young back then.

EDIT: Not technically monsters per se, but red players in UO were fucking terrfying to my craft centric/solo playstyle.

These fucking assholes would level up, roam in bands, murdering other PCs for fun, and take their stuff until their faction loss was enough to make ther name turn from blue to red. I used to always lose my shit when I saw one. Enough so that I maxed out my hide skill even though I wasn't a thief or anything.

Oddly enough, the equivalent in other MMOs never had quite the same effect.

EDIT 2: I miss real MMOs....well kind of. Aint nobody got time for that now.

 

[Ultra]

For those who might not know this little shit would pilfer random items (even ones required to progress!) and make off. He was quick and could easily kite you halfway through a dungeon you haven't yet mapped and into packs of other monsters.

 

[Ellef]

Rust monster. Strike at the very heart of what it means to be an adventurer.

 

[Wayward Son]

My first encounter with beholders in DnD (I forget the edition). All my DM would say is "Watch out for the beholders" and I had no clue whatsoever what he meant. Then I encountered one on my way to the first dungeon he sent me to. He showed me the picture out of the Monster Manual. And then promptly killed me off. He then asked, "So, how'd you like DnD?"

 

[Alex]

Rust monster. Strike at the very heart of what it means to be an adventurer.

Don't forget level draining undead while you are at it. And if your DM knows what he was doing, a lich is always really bad news.

 

[animlboogy]

 

[Goral]

Almost as scary as aliens in AvP. Their looks aren't that scary but the sound they're making...

 

[Sykar]

Mudcrabs.

 

[Ruhfuss]

 

[octavius]

Duriel in Diablo 2 was something I always dreaded facing, especially with an Archer.

For those who might not know this little shit would pilfer random items (even ones required to progress!) and make off. He was quick and could easily kite you halfway through a dungeon you haven't yet mapped and into packs of other monsters.

And to make matters worse, he had a rage inducing laugh everytime he nicked an item.

 

[Astral Rag]

Moira Brown

 

[Unkillable Cat]

Rust Monsters are for pussies, Living Mucks is what should scare people.

Any item touched by a living muck needs a saving throw (vs acid) or be destroyed. (That means attacking one costs you your weapons.)
Immune to acid, lightning and poison.
Half damage from fire and magic missiles.
Can squeeze through cracks at least 1 inch wide.
Can climb walls and ceilings.
Paralytic touch.

Basically it's a blob of acid that wants to eat you.

 

[Jack Of Owls]

For those who might not know this little shit would pilfer random items (even ones required to progress!) and make off. He was quick and could easily kite you halfway through a dungeon you haven't yet mapped and into packs of other monsters.

I do not have the breadth of knowledge necessary to have a valid oppinion on which RPG this monster was from, but I'm guessing it's from one of the early Wizardry entries? Did you at least have a chance of catching him later in the dungeon and reclaiming your lost items? Otherwise that would really suck.

Someone mentioned level-draining undead but I never really feared them much in DnD games because I was always prepared and well-stocked with a Restoration spell or potion or two.

 

[Dorateen]

Wights.

One of the first undead low level characters run into that can drain levels. I hate losing levels.

 

[Eirikur]

 

[Neanderthal]

A Grue.

Obviously.

 

[Mozg]

Jackals in ADOM

Actually jackals are more memey but in real games it was pink and cyan spiders that really drowned you.

A similar situation was the worst versions of the fungal infestation in some iterations of Crawl. Whole levels became danger zones you could never pass through normally again.

 

[Ultra]

For those who might not know this little shit would pilfer random items (even ones required to progress!) and make off. He was quick and could easily kite you halfway through a dungeon you haven't yet mapped and into packs of other monsters.

I do not have the breadth of knowledge necessary to have a valid oppinion on which RPG this monster was from, but I'm guessing it's from one of the early Wizardry entries? Did you at least have a chance of catching him later in the dungeon and reclaiming your lost items? Otherwise that would really suck.

Someone mentioned level-draining undead but I never really feared them much in DnD games because I was always prepared and well-stocked with a Restoration spell or potion or two.

It's from Dungeon Master an old Atari ST and Amiga blobber but real time and yeah if you catch and kill the little dude you get whatever he snatched up back. Apparently he's known in game as a 'giggler' and can actually only steal items held in a party members hands which I never knew!

 

[Taka-Haradin puolipeikko]

Those bloody fucking karmic lizards in ADOM.

Never had problems with jackals.

 

[Gregz]

Purple worms, rust monsters, beholders, anything with level drain...mind flayers are pretty bad too

Edit: Yeah, and this fucker

and these: