Whats your favorite RPG with a roll under core mechanic and why?

[ZhakirSetie]

I've found myself interested in playing an rpg with roll under core mechanics lately. I know of a handful; Gurps/Hero System, Call of Cthulhu/Mythras, and Modiphius 2d20s, but I'm interested in your favorite (if you have one) and why it's your favorite versus other ones.

So how bout it? Any with interesting mechanics? Streamlined or complex?

[MoiMagnus]

"Le Donjon de Naheulbeuk"
As the name suggest, it's a French TTRPG, and sadly for the international audience, only available in French.

Mechanically, it inherits a lot from "The Dark Eye" (aka "Das Schwarze Auge"), including the "roll under with a d20", but to be honest, the mechanics are not really the reason why it's a good RPG.
The point of the RPG is that it is a parody.
(1) The universe is almost self-aware: dungeons are handled by individuals dungeon masters that obtained a licence from the dungeon master guild. Adventurers successfully going through those dungeons are taxed by the guild, which funds the dungeon masters that follows the guidelines for "level-appropriate dungeons" (while level-up are granted by some metaphysical administration).
PS: The universe is more on the dystopic side, so the "good guys" are the ones that are usually the most screwed in this equation. Well, and evil sbires like goblins too, their death rate is even higher than the heroes' death rate, which is a high bar.
(2) Every class/race/god/magic is designed to be one most stupid stereotype you could find. For example "Fall into traps" is an innate feat for wood elves, and one of the magic school is called "Thermodynamics" and start with spells like "cooking an egg".
(3) The system is designed for "heroes" to be incompetent at low level. This combined with the incompetence of low level enemies mean that it's not uncommon for "friendly fire" to be responsible for more damage than the actual enemies.

[Also, it's free http://www.naheulbeuk.com (http://www.naheulbeuk.com/index.htm). As for its origin, "Le Donjon de Naheulbeuk" was initially a MP3 series in a parodic D&D-like universe. A little like early OOTS, but with a more middle-school / high-school humour. The series was then reverse-engineered into a TTRPG by its creator.]

[Quertus]

Shrug. My favorite roll-under system was a homebrew titled "Paradox" (think Rifts, but good). But my love of the system had nothing to do with the roll-under mechanics, and afaik it wasn't published / doesn't exist online, so I'm not sure how much this information will help you.

[Mastikator]

Drakar och Demoner: Trudvagn, it's only in Swedish and defunct. I blame D&D for devouring the entire TTRPG scene.

I especially liked the way combat was handled, each time you attacked someone you allocated a number of combat points (max 19) and rolled a d20, if you roll below you hit.
Your combat points came from your combat skill plus your combat specialization (for example you could have a +5 to swords, so you have 5 more if you use a sword, or +5 to shields, which would then only be useful for shield bashing or blocking, there were also general ones for attacking and blocking). If you saved points you could then use them as a reaction to block attack.

It also had exploding damage dice, every weapon simply did a 1d10 damage, two handed weapons did 1d10+2, if you had a strength modifier you also added that. Then if you rolled a 10 you rolled again and added that, some weapons had a explosion range of 9-10, some even 8-10. There was one exotic weapon with 7-10, and you could have combat specializations that also increased the range but costed combat points to use.

[Anonymouswizard]

Unknown Armies. It's the setting

It's set in the modern world, where magic exists. However this isn't your standard wizard magic.

Magick is postmodern.

All magick is thematic and based on a paradox. Maybe you build cockatiel devices, a vision of the future rooted in the past. Maybe you make movie clichés real. Maybe you get really drink. But if you're an Adept you follow a theme, do actions to charge up, and cast spells, while avoiding your Taboo active or situations because it robs you of your mojo. If you're an Avatar you Abby in accordance with an Archetype to get powers associated with it but have to avoid your Taboo. And outside of those it gets even more crazy, there's at least one ritual to leave your life behind and start again.

We also have our mystic conspiracies! They're small, 100 is considered unwieldy, and even the strongest forces in the occult underground couldn't stand up to any muggle powers. But they have goals, whether that's create a new age of magick via a global fast food chain, become the ones in control of the magick, or make a giant database on your citizens to help track terrorists, they have members, and they have resources. Your group is most likely smaller, but there's advantages for that and nobody has a Monopoly on coming.

System wise I'm going to focus on 3e. It's d%, roll under roll high, with incredibly lethal combat. The combat Arctic behind on succeeding six other things that the characters could do. The core of your character are your Shock Guess, which includes you're Failed notches (how close to a breakdown you are) and your Hardened notches (how deadened you are to stimuli) in the categories of Violence, Unnatural, Helplessness, Self, and Isolation. Each is attached to two skills, at one hardened nich your nice healthy skill begins at 60 and your emotionally dead skill begins at 20, every hardened nich gives you an additional 5% in your unhealthy skill while reducing your nice healthy skill by 5%.

Thus the more you detach from humanity the less able you are to interact normally, and the changing skill scores push players towards such behaviour.

Each Shock Guage attacks one of the others and defends another, but I forget how it works.

Identities are progressions or the like that sub for at least one skill, maybe do two other things, and represent who your character is. They let you remain good at your niche even after you've gained notches. United they let you cast magick.

[Telok]

Last edition of Paranoia was a nice d20 roll under. It went blackjack style so higher rolls beat lower rolls but you still had to be under your skill number. Even better the only math in the system was in combat where damage was margins of success based on the weapon to assign narrative wound levels. And there was a hack to remove even that math. One die, no math.

[The Glyphstone]

The only roll-under system I'm familiar with is the FFG line of Warhammer 40K RPGs. At least in the normal-people range of games - Only War and Dark Heresy mainly - your low stats on a d100 system mean you're innately going to fail at almost everything, unless you abuse circumstance bonuses. So in a sort of roundabout way, it encourages scraping and sneaking your way into every advantage possible, like a sensible person in the Warhammer universe would have to.

[olskool]

For percentile games it's The Design Mechanism's MYTHRAS all the way. A very easy to use system based on Runequest/BRP. The Special Effects are fun in combat and the game is Skill-Based. I also love the ACTIONS based initiative. A cheaper (less polished) version would be Mongoose Publishing's LEGEND.

For a D20 roll under, I have a soft spot for GDW's old system used in Twilight2000 v2.2 and Traveller The New Era. In this system, the player combines an Attribute (or Attributes) rated from 1 to 10 like STR or INT with a SKILL rated from 0 to 10. This combined number was called an ASSET and is the chance to perform an AVERAGE task on a roll of a D20. The skill could then be modified based on a task's difficulty.

EASY TASKS: 2 x Skill Asset
ROUTINE TASKS: 1.5 x Skill Asset
AVERAGE TASKS: Skill Asset
FAIRLY DIFFICULT TASKS: 0.75 x Skill Asset
DIFFICULT TASKS: 0.5 x Skill Asset
FORMIDABLE TASKS: 0.25 x Skill Asset
IMPOSSIBLE TASKS: 0.1 x Skill Asset

The system is fast and easy to use.

[gijoemike]

Villains and Vigilantes: Mighty Protectors. A superhero game currently in its 3rd edition.

Roll a d20 always wanting to go low for attacks and saves. the Target's Armor modifier just adds to your roll making it harder to hit them. negative values to a roll are usually a good thing.

[Eldan]

Unknown Armies. It's the setting

It's set in the modern world, where magic exists. However this isn't your standard wizard magic.

Magick is postmodern.

All magick is thematic and based on a paradox. Maybe you build cockatiel devices, a vision of the future rooted in the past. Maybe you make movie clichés real. Maybe you get really drink. But if you're an Adept you follow a theme, do actions to charge up, and cast spells, while avoiding your Taboo active or situations because it robs you of your mojo. If you're an Avatar you Abby in accordance with an Archetype to get powers associated with it but have to avoid your Taboo. And outside of those it gets even more crazy, there's at least one ritual to leave your life behind and start again.

We also have our mystic conspiracies! They're small, 100 is considered unwieldy, and even the strongest forces in the occult underground couldn't stand up to any muggle powers. But they have goals, whether that's create a new age of magick via a global fast food chain, become the ones in control of the magick, or make a giant database on your citizens to help track terrorists, they have members, and they have resources. Your group is most likely smaller, but there's advantages for that and nobody has a Monopoly on coming.

System wise I'm going to focus on 3e. It's d%, roll under roll high, with incredibly lethal combat. The combat Arctic behind on succeeding six other things that the characters could do. The core of your character are your Shock Guess, which includes you're Failed notches (how close to a breakdown you are) and your Hardened notches (how deadened you are to stimuli) in the categories of Violence, Unnatural, Helplessness, Self, and Isolation. Each is attached to two skills, at one hardened nich your nice healthy skill begins at 60 and your emotionally dead skill begins at 20, every hardened nich gives you an additional 5% in your unhealthy skill while reducing your nice healthy skill by 5%.

Thus the more you detach from humanity the less able you are to interact normally, and the changing skill scores push players towards such behaviour.

Each Shock Guage attacks one of the others and defends another, but I forget how it works.

Identities are progressions or the like that sub for at least one skill, maybe do two other things, and represent who your character is. They let you remain good at your niche even after you've gained notches. United they let you cast magick.

This. This is basically the post I wanted to make. Great setting, great system.

[Anonymouswizard]

This. This is basically the post I wanted to make. Great setting, great system.

Apart from all those horrendous typos, obviously.

When I'm back from this afternoon's tasks I'll clear it up.

[hifidelity2]

I would say
GURPs - as the system has less chance of criticals / fumbles due to the use of 3D6 rather than 1 D20
RuneQuest - As I like the setting / mythology

[Ettina]

I've only tried one, Call of Cthulhu. Run a single session and had fun. The roll under mechanic is interesting, especially with stats that are expected to decrease like sanity and luck. It's a neat way to create a downward spiral for sanity.

[Kapow]

It has been mentioned in passing, The Dark Eye (Das Schwarze Auge) will always have a place in my heart.
Probably this is due to nostalgia in no small way, as it was the first rpg I played 30 years ago.
It IS crunchy.
But I like the way they handled skills and spells - basically you have to roll under three attributes (sometimes two times the same) and can use your skill-/spellpoints to compensate, if you were rolling to high. The more skill-/spellpoints you have left the better.
Combat is an attack roll vs parry or dodge.
Compared to DnD it has a much flatter power curve and a lower ceiling.

It also has a really dense and detailed setting, although we never used it that much and made it our own.

[Lord Torath]

2nd Edition AD&D Psionics. You want to roll as high as possible without going over your target number, rather like in the old TV game show The Price is Right (in which we find out how many playgrounders are old like me - I used to watch it when I stayed home sick form school). Opposed checks are a breeze to resolve: highest successful roll wins. You usually get an extra bonus if you hit the target exactly. Nat 20 is a critical failure, and nat 1 is frequently a success with complications.
I love the ease of resolving opposed checks. I've adopted that method for use with NWP and ability score checks as well.

That's it as far as d20 'roll unders' for me.

I've played a one-shot of Runequest, which is roll-under on a d100. Not enough experience to form an opinion.

I've played about five sessions of FFG Deathwatch, which is rather similar to the Dark Heresy and Only War mentioned by The Glyphstone above, except with about 10 points added to your target numbers (typical gear and abilities add +10 to +20 on top of that for particular tests). I wanted to implement the "Price is Right" method for this one, but with the situational modifiers, you can get target numbers over 100, and that makes it hard to implement. Degrees of success are important, which is how many "tens" you beat your target number by, so just having a target number over 100 does not guarantee a full success - although it frequently does.

[noob]

"Le Donjon de Naheulbeuk"
As the name suggest, it's a French TTRPG, and sadly for the international audience, only available in French.

Mechanically, it inherits a lot from "The Dark Eye" (aka "Das Schwarze Auge"), including the "roll under with a d20", but to be honest, the mechanics are not really the reason why it's a good RPG.
The point of the RPG is that it is a parody.
(1) The universe is almost self-aware: dungeons are handled by individuals dungeon masters that obtained a licence from the dungeon master guild. Adventurers successfully going through those dungeons are taxed by the guild, which funds the dungeon masters that follows the guidelines for "level-appropriate dungeons" (while level-up are granted by some metaphysical administration).
PS: The universe is more on the dystopic side, so the "good guys" are the ones that are usually the most screwed in this equation. Well, and evil sbires like goblins too, their death rate is even higher than the heroes' death rate, which is a high bar.
(2) Every class/race/god/magic is designed to be one most stupid stereotype you could find. For example "Fall into traps" is an innate feat for wood elves, and one of the magic school is called "Thermodynamics" and start with spells like "cooking an egg".
(3) The system is designed for "heroes" to be incompetent at low level. This combined with the incompetence of low level enemies mean that it's not uncommon for "friendly fire" to be responsible for more damage than the actual enemies.

[Also, it's free http://www.naheulbeuk.com (http://www.naheulbeuk.com/index.htm). As for its origin, "Le Donjon de Naheulbeuk" was initially a MP3 series in a parodic D&D-like universe. A little like early OOTS, but with a more middle-school / high-school humour. The series was then reverse-engineered into a TTRPG by its creator.]
I played it a bit and I can tell you: to avoid friendly fire just do not shoot at things when there is allies remotely close to the line between you and the opponent. (why would you do that anyway? I am pretty sure I would not try to do that in real life)
As for thermodynamic magic being its own school it makes more sense than doing catch all schools like "turn something in something else Or alter its properties Or change the rules of physics over here Or unnaturally alter what something is made of without altering its function"(dnd 3.5 transmutation)


PS: The universe is more on the dystopic side, so the "good guys" are the ones that are usually the most screwed in this equation. Well, and evil sbires like goblins too, their death rate is even higher than the heroes' death rate, which is a high bar.
It is the case in many rpgs including Call of chtulu (seriously if you are an evil guy you are probably going to summon a creature which will bash your head in or eat your consciousness or something while the best a good guy obtains is a temporary victory at extreme costs)

[EggKookoo]

I think the only roll-under system I've ever played was Call of Cthulhu.

[Grod_The_Giant]

STaRS. Because I wrote it ;)

Mechanically, it's a generic 1d10 roll-under-your-ability-score thing, combined with a "players roll all the dice" approach and (in combat) damage based on degrees of success/failure. The net effect is lightning-fast combat, since there's virtually no back-and-forth with the GM--you know the results of your action the second the die stops bouncing.