Instakill Mechanics in TTRPGs

[Laurefindel]

Does anyone have any experience with instakill rules from other TTRPGs? Did they allow assassin-type PCs to really feel like assassins, or did the instakills feel cheesy and unbalanced? Are instakill rules even wise to have in TTRPGs, or are they too prone to being abused?

I've seen many RPG where enemies can (relatively) easily be instakilled, but they tend to fall in two categories.

Asymmetric systems: NPCs and enemies are not all made like PCs. Minion rules with 1 hp that will drop regardless what hit them for example, or systems that assume that PCs will prevail automatically without any roll. 7th Sea 2e has an advantage that characters can purchase where the "scene" opens on an unimportant NPC who hear a "pssst!", turns around to investigate, disappears behind a door/alley, emits a unintelligible muffled cry, and the PC reappears instead wearing the guard's clothing. Generally, PCs cannot as easily be eliminated in one shot in those systems.

Symmetrical Systems: PCs and NPCs can be dropped in one shot in the same fashion, typically because of some sort of critical hit effect, some sort of massive damage rule, a class-specific or monster-specific ability, or by virtue of hp remaining low throughout the game. Note than many games differentiate between instantly dropping out of combat (but not necessarily dead) and instantly dropping dead. In The One Ring (1st ed) RPG, armor acts as a saving throw vs wounds on a critical hit (a piercing blow). If you score a piercing blow and the oppoenent fails their armour test; they drop instantly. PCs and some adversaries have addtional layers of protection. For example, a PC falls unconscious if they fail that armor save twice, and if the attack that caused the final piercing blow also drops them to 0 endurance, they are killed outright.

As for whether it is wise or not; it depends. The fact that enemies can fall in one shot will set the tone of the game. The fact that PCs can fall in one shot will set that tone even further. Personally. I prefer systems where combats against "minions" don't drag on unnecessarily. Having them potentially hit hard but fall easily is often preferable, even if it can be cheesed ocasionally.

 

[John Dallman]

I found a way to get the overall result in GURPS WWII, where it's fairly difficult to actually kill people in one attack without a rifle. You don't usually kill in one attack, but if it works, your target is prevented from making much noise and at sufficient penalties that you can finish them off. It's simplified from a routine in GURPS Martial Arts: Fairbairn Close Combat Systems. William Fairbairn was an instructor for the Shanghai Municipal Police before WWII, then for MI6, the British Commandos, the Special Operations Executive and the US Office of Strategic Services. He's also the "Fairbairn" in the Fairbairn-Sykes fighting knife.

You need decent strength and dexterity, excellent Stealth skill, decent Knife skill, and a Balanced Very Fine knife for the +1 to hit and +2 damage. A Weapon Bond perk for your knife is also helpful for another +1 to hit. You also need your target to be alone with nobody watching them, which is usually fine for lone sentries. If it's night-time, which it usually will be, the Night Vision advantage is very helpful.

1. Use Stealth to approach them from behind, and get to 1-yard range without being spotted.
2. Use Evaluate for up to three seconds, for +1 to hit with the knife per second.
3. Step and All-Out Attack (double). This is the risky part: you need to make two simultaneous attacks but it means you're defenceless if anyone attacks you.
4. The first attack is a right-handed Telegraphic Attack (+4 to hit, easier to dodge, but that doesn't apply if the target gets no defence due to being completely surprised), to the jaw (-6 to hit, but that's halved for grappling), using dexterity, rolling against DX+1. If you hit, you have grappled the jaw and can hold the target's mouth shut.
5. The second attack is a left-handed Knife stab to the vitals (-3). That's at Knife-3, +1 for the Balanced knife, plus any Weapon Bond, plus your Evaluate bonus (which cannot be used on a Telegraphic Attack).
6. Assuming you hit with the stab, you do Strength-based Thrust damage, +2 for the Very Fine knife. With Strength 13, a plausible level for a realistic commando, that's 1d6+2, 3-8 damage. It's tripled after armour because you stabbed the vitals, and almost nobody wears body armour in a WWII setting, because it's expensive and ineffective against rifle fire. So you do between 9 and 24 points of damage.

9 points is a Major Wound on any realistic human, and since it's to the vitals, requires the target to make a Health-5 roll or be knocked down and stunned. If they fail that roll by 5 or more, they're unconscious. Even if the target succeeds in the Health-5 roll, they're at -4 to do anything because of the shock penalty, for being injured and the attacker's best move is to hold onto their jaw and stab them again. You haven't one-shotted them, but you've put them a long way into the GURPS death spiral with a surprise attack. All of this can be used by NPCs against PCs, but most NPCs don't have the skill levels required to make it semi-reliable.

Yes, this involves complicated rules and difficult rolls. It also demands careful thinking about the physical environment in the area. You end up identifying more closely with the character and their feelings. And for me, that's a key part of role-playing.

 

[Gorgon Zee]

I have been working on a TTRPG of my own (who hasn't?), and one interesting hurdle I bumped into was how to make the rules facilitate a satisfying assassin playstyle. That is, for a character to be able to sneak up on a creature and swiftly and silently take them out in a single, well-prepared moment.

I was about to say "this depends on the system", but then I realized that actually I use pretty much the same technique for all systems! So ...

For simple assassinations, this is a simple check. Choose as skill / background, whatever and do it:

• In Everyway, check opposing elements and if there's any doubt, draw a card and interpret
• In Fate Core, set the difficulty of the obstacle, and let the player attempt to overcome it to succeed
• In D&D4E, skill check vs. TN

For a full scene, I would use a modification of D&D4E's skill challenge. The GM defines a set of obstacles that must be overcome in order to achieve the goal (in this case, assassination). Some might be ones that must be overcome to succeed, others are ones where so long as you get N successes you are good. M failures will fail the whole challenge. Each system then just uses its own action resolution system for the individual choices.

I'll give an example for Pelgrane's 13th Age in which I have actually played an assassin and so had "Assassin of the Black" as my background which I could for pretty much all these:

Challenge: Assassinate the Vice-Chancellor
5 successes (2 mandatory) before 3 failures

(Mandatory) Establish a location where she is alone (Int or Wis)
(Max 2) Observe their movements (Int, Dex)
(Max 1) Disguise yourself (Cha)
(Max 2) Build an exit plan (Int)
(Max 2) Remove retainers / guards (Cha or 30gp bribes)
(Mandatory, must have 4 previous successes) Make the Killing Blow (Weapon attack)

 

[Benjamin Olson]

I think the biggest barrier here is that you seem to be in a 5e mindset of bloated HPs, where major enemies would also be high-level, tough warriors. It doesn't have to be like that, and that sort of rules approach has unfortunate lore consequences. Sure adventurers are built different, but 3 weeks of adventuring and suddenly you can shake off injuries that would kill a normal human; 3 years and you have orders of magnitude more toughness than most people. The head of every organization is always a high level combatant rather than just someone good at manipulating people or some rich guy. The reason it is hard to assassinate a head of state in real life is not generally that they are a retired adventurer with 18 levels of Wizard.

But if you're deep into game design already around 5e-esque HP model, I think your best bet is giving the assassin some sort of sneak attack style extra dice and autocrit ability. If you bake some sort of sneak attack extra dice against helpless opponents right into the core rules and available for all players and NPCs then you also avoid the bloated HP absurdity of "someone's got a knife to my throat and I don't even care, it's just a d4 of damage".

 

[Li Shenron]

I have been working on a TTRPG of my own (who hasn't?), and one interesting hurdle I bumped into was how to make the rules facilitate a satisfying assassin playstyle. That is, for a character to be able to sneak up on a creature and swiftly and silently take them out in a single, well-prepared moment.

Sure, you can simply have a rogue/assassin character deal a decent amount of damage in a single hit (a-la D&D5e sneak attack), but the amount of bonus damage is typically not enough to kill a guard in a single hit, and that seems necessary for balance reasons. Since the damage is not enough to take them out instantly, they can then call for help and your assault feels less like an assassination attempt and more like a decent opener for a combat encounter you were hoping to avoid entirely.

Does anyone have any experience with instakill rules from other TTRPGs? Did they allow assassin-type PCs to really feel like assassins, or did the instakills feel cheesy and unbalanced? Are instakill rules even wise to have in TTRPGs, or are they too prone to being abused?

D&D history is full of insta-kill rules, like save-or-die effects...

The problem is not which rule you use but rather the fact that as soon as you have a rule because you want the PC to insta-kill irrelevant NPCs, the players have a rule to also insta-kill very relevant PCs, which you don't want.

Just allow PCs to kill irrelevant NPCs by giving them few HP. In 5e the Assassin Rogue ability is simply an autocrit on a surprised foe. When you factor sneak attack in, even a low level assassin is almost guaranteed to kill a surprised commoner on a hit.

 

[jian]

I think that there are multiple solutions here. As you say, D&D etc can give you massive damage on sneak attacks which can kill a guard if their HP is low enough, and so it's a question of tweaking that differential. The question then is the level difference - should a 1st level assassin be able to one-shot a CR 0.5 guard? Should a 5th level assassin be able to one-shot a CR 1 guard? And so on.

Plenty of games basically let you take out mooks with a single successful hit, sneaking or not. These mostly don't use HP or similar. An example might be Cortex Plus where, if you're playing in a Tenchu: Stealth Assassins* type setting, this might be the balance of stats:

• The PC: Onimaru the ninja assassin has Duty d10, Sneaky d8, and Ninja Assassin d8. He rolls those three dice and takes the highest two as his result.
• The guard: The guard is part of a Challenge Pool for infiltrating a heavily guarded compound so that Onimaru can assassinate the target, a fearful samurai retainer who owes a lot of money to the local yakuza. The Challenge Pool is 4d8, Watchful Guards d6, Lanterns Everywhere d8.

When Onimaru tries to kill a guard to facilitate his mission, he rolls d8, d8, d10 and keeps two. The GM rolls d6+d8. If Onimaru succeeds, he kills a guard and reduces the Challenge Pool to 3d8; once he's done this four times and reduced the Pool to zero dice, he can reach the samurai and have the scene where he tries to assassinate him. If Onimaru fails a roll, he takes a d8 Complication, such as Injured d8 or The Guards Know I'm Here d8.

*My personal favourite ninja game; the first game is a genuinely great cinematic ninja simulator

 

[Blue]

The crunchy fantasy ruleset I'm working on (as opposed to the narrative ruleset I'm working on) has multiple tier of expendables, which are used for everything from HPs (for a variety of things, not just physical damage) to effort used to power actions.

If you have someone helpless, such as asleep or with a sword to their throat, they don't get to defend and you can do damage against the highest tier you can. So a hero can't one-shot a dragon, but you can insta-kill (or insta-unconcious even easier) someone of lesser stature.

 

[Blue]

One of my RPG design conundrums is allowing instant-kills (in the type of game where death is a common stakes for a challenge), but not have it used against the players in a way that's unfun, while still not feeling like they are protected by plot armor.

Insta-kill/knockout only against weaker opponents partially satisfies this, but a foe hiring a legendary assassin is a trope of the genre.

 

[Gorgon Zee]

One of my RPG design conundrums is allowing instant-kills (in the type of game where death is a common stakes for a challenge), but not have it used against the players in a way that's unfun, while still not feeling like they are protected by plot armor.

Insta-kill/knockout only against weaker opponents partially satisfies this, but a foe hiring a legendary assassin is a trope of the genre.

PF2 has a nice feature for this, called incapacitation. If a spell has this feature, then any result (crit fail, fail, success, crit success) is adjusted one level down when used against someone of higher rank.
So if you wanted an assassinate power in PF2, I might make one like this:

Assassinate
Focus power 3 actions • Incapacitation • Not usable in combat • Requires a deadly weapon • opponent must be unaware of you
Make a regular weapon attack:

• Crit fail: The target is alerted and can make a free move action and a free action to call out for help.
• Fail: Your attack fails; The target is alerted
• Success: Roll critical damage.
• Critical Success: Target is given a mortal wound and is unconscious. If attacked again or not given first aid within three rounds, target dies.

So it is effectively impossible to instakill higher level targets, and even for lower level ones, you have to spend a whole round doing so, and have them unaware and have no friends nearby to heal you if you do get dropped.

 

[Celebrim]

I dislike insta-kill rules, but I also had a situation in my D&D campaign where a hasted 10th level rogue achieved surprised on a high level half-sahuagin cleric and killed them (about 86 hit points) before the cleric could react.

I generally disapprove however of low-level characters being about to one shot a higher-level character that aren't helpless for some reason. And in general, I steer the game away from being able to easily one shot any character because I tend to use symmetric rules. Anything that can happen to an NPC can happen to you.

So for example, Storm Troopers in my Star Wars RPG are pretty darn hard to kill and will normally take several blaster bolts to die (most Storm Troopers "dying" on screen are just stunned, wounded, or knocked unconscious, or at least the ones not actually ripped apart and eaten by sentient arboreal bears that are pound for pound as strong as chimpanzees).

I prefer to play a homebrew version of 3e, and something like a 1st level hobgoblin fighter will typically have 15 hit points, a zombie has like 32 hit points, and an Ogre has like 42. Typically nothing goes down in less than 3-5 rounds unless its way under your CR.

1e AD&D famously has a "house cat problem" where a house cat could easily kill several human farmers. I don't really have a house cat problem in my games, but I do have a "white tailed deer" problem where hunting large game with a bow seems like it should be basically impossible. Whether this is good or bad is a different question. If my opinion a system that drops NPCs quickly will also drop PCs quickly, and that's not at all desirable.