Instakill Mechanics in TTRPGs

[zarionofarabel]

So I'm not going to let a movie define what the "One True Narrative" is about an RPG setting.

Well, I want a TTRPG to emulate the media it represents, and the media is the movies and TV shows. In the movies and TV shows Stormtroopers die after taking a single blaster hit, so that's what I want in a game, simple as that.

I don't agree with you about D&D. So we are probably miles apart on this.

If you mean that I think D&D (all iterations) are abysmal TTRPGs, then yes.

 

[zakael19]

"I don't want the thing that created the setting to define the cadence and tropes of play within the setting" is certainly one way to approach things.

As an aside, generally concur with all the other posters here who have noted that "assassin" style of play focused insta kill mechanics generally create terrible table play in a conventional RPG game.

 

[aramis erak]

The problem with this is the lack of hit points in Star Wars D6. If I implement a world where blaster bolts from basically any weapon are actually killing Stormtroopers on a single hit, then the overlap between armored stormtrooper's soak and a PC's soak is pretty strong. In the lore we don't see a lot of protagonists wearing armor, which is fine, we can explain via system mechanics why you might want to avoid heavy armor. But it then creates a world where if blaster bolts are one shotting armored stormtroopers they are very likely to be one shotting PCs as well.

WEG stormtroopers have 3d soak (STR+Armor); blaster rifles have 5D damage. Averages 10.5 and 17.5 ... under 2e, that's usually a wound, sometimes incapacitated, in the 4-8 over range; 9-12 is incapacitated. Under 1e, it's usually about 1.5, so in the DR>=1*SR, also a wound, with DR >=2*SR being incapacitated.
Either edition, it's pretty common to need a double-tap, but about 1 in 4 shots is straight to incapacitated.
I'll note that in 1E, DR>3*SR is mortal, as is 2E margin of 13+.
If using 2e, it's possible to push your blaster's damage up to 6d+2 (if you're willing to put the XP into it) and drop ST's left and right... as 23 average damage is usually mortal.

 

[Minion X]

Wouldn't you need to immobilize the target and cover their mouth to ensure a quick and quiet kill? In D&D this would be covered by grappling.

 

[kronovan]

AD&D has an Assassin class as a sub class of Thief. When the Assassin attempts a kill, it uses a special Assassin's table(DMG p 75). No damage worries at first. Just a % chance of instant kill that varies based on target level and assassin level. If the instant kill fails, you calculate weapon and/or poison damage and proceed. Possible that damage will kill the target even if the Assassination attempt fails...

Old School Essentials has a similar assasination rule for its Assassin. For it, if the Assassin can attack an unaware Humanoid from behind, they get a +4 bonus to hit. If successful the target must make a Death save, with a failure resulting in death. Where a table comes into play, is there's a column on the Assassin Skill Chance of Success table that contains a penalty for the target's death save; 0 for up to class level 3, but then a penalty that increases every 2 levels.

The big challenge in OSE is actually being able to attack a humanoid from behind while they're unaware. The chance of success on the ASCoS table for Hide in Shadows or Move Silently skills are very low - don't get anywhere near reliable until about level 8. IME as both player and referee, the chance of catching a NPC unaware at lower class levels comes more from narrative play, when the player can make a convincing argument based upon circumstances. Which isn't necessarily a bad thing considering the lethality of it. I played an Assassin nd in early play, played for 6 sessions before I could pull off an assassination.

The rule is for Humanoids, but I and some of my referees, would allow it for some monsters.

 

[GraveDev]

Very interesting takes and experiences from people so far!

As a small update; I decided to attempt to implement instakill mechanics into my system through a condition called Off-Guard.

Essentially, if an entity (creature) is not actively guarding its space, or is unconscious, they are Off-Guard. The condition grants incoming checks versus the entity some bonuses, and if they take damage in a single turn that is equal to or greater than half their maximum HP, they instantly die. When they take damage, or are otherwise alterted to danger, they are no longer Off-Guard at the end of the turn.

For context, the system has HP values that are typically around 10 - 60 for most entities, except for weak minions and bosses. Attacks typically deal on average ~7 damage without any buffs, and so PCs can reasonably deal up to ~30 damage in a single turn if they invest resources into the attacks.

The design intent for the instakill rules is to enable assassinations, but without it cheesing tough opponents. With the Off-Guard condition, an assassin PC could very reasonably assassinate most average entities such as 30-40 HP guards and 10-20 HP bandits, without being able to nova down a boss with 100+ HP.

 

[Tigris]

Very interesting takes and experiences from people so far!

As a small update; I decided to attempt to implement instakill mechanics into my system through a condition called Off-Guard.

Essentially, if an entity (creature) is not actively guarding its space, or is unconscious, they are Off-Guard. The condition grants incoming checks versus the entity some bonuses, and if they take damage in a single turn that is equal to or greater than half their maximum HP, they instantly die. When they take damage, or are otherwise alterted to danger, they are no longer Off-Guard at the end of the turn.

For context, the system has HP values that are typically around 10 - 60 for most entities, except for weak minions and bosses. Attacks typically deal on average ~7 damage without any buffs, and so PCs can reasonably deal up to ~30 damage in a single turn if they invest resources into the attacks.

The design intent for the instakill rules is to enable assassinations, but without it cheesing tough opponents. With the Off-Guard condition, an assassin PC could very reasonably assassinate most average entities such as 30-40 HP guards and 10-20 HP bandits, without being able to nova down a boss with 100+ HP.

Are you going to use the Off Guard condition also for other things?

I just ask because I normally prefer having an "elegant" design with phewer, but repeated, mechanics, but it may be a bit hard here since you want it for assassination.


Is this only for the assassin? Or a general mechanic?


I dont have a better suggestions, was just thinking of something that the off guard condition could be something a bit more generic as an example "if a character is off guard and they become bloody they are stunned for 1 turn" or something around.


And the assassin can KO a stunned bloodied enemies when next to them. (With big enemies being imune to stun). With some additional damage about unsuspecting enemies.


So off guard could be something also be used in combat to "sucker punch" enemies and lasts until damaged.

 

[Willie the Duck]

For context, the system has HP values that are typically around 10 - 60 for most entities, except for weak minions and bosses. Attacks typically deal on average ~7 damage without any buffs, and so PCs can reasonably deal up to ~30 damage in a single turn if they invest resources into the attacks.

The design intent for the instakill rules is to enable assassinations, but without it cheesing tough opponents. With the Off-Guard condition, an assassin PC could very reasonably assassinate most average entities such as 30-40 HP guards and 10-20 HP bandits, without being able to nova down a boss with 100+ HP.

In reference to:

I say this because mechanics that instead allow a sneaking assassin types to do huge amounts'* of hit points when they sneak up on someone tend to have the side effect of being really powerful opener'** in regular combats. Unless that's the tactical gameplay element you are going for ('let's arrange things so all combats start with Joe's character hidden and with first initiative.' 'there's the enemy assassin, someone glitterdust it before it can hide again!').
*relative to the opposition, see zarionofarabel's Mythras example.
**or ongoing challenges, if they can hide or otherwise get the drop on people again.

The question for me is: Are there going to be a lot of encounters where the enemy group is lead by a 50-60 HP guard captain? If so, is the optimum strategy for the PCs now going to be 'sneak the party assassin in there to get the drop on the most high-value target before they know they are in combat?' If so, how often, and is do you consider this a feature, bug, or neutral emergent property of the game design?

 

[SpellObjectEnthusiast]

IME as both player and referee, the chance of catching a NPC unaware at lower class levels comes more from narrative play, when the player can make a convincing argument based upon circumstances.

This is generally true in B/X for just about everything. Convincing your GM you find the secret door through "narrative interaction" is always going to have better odds than rolling a 1 in 6, convincing an npc using your own words is better than rolling under cha, etc etc. That's kinda the bedrock behind the modern OSR playstyle.

 

[mmadsen]

Are instakill rules even wise to have in TTRPGs, or are they too prone to being abused?

Ablative hit points make it very, very hard to kill someone in one blow -- or very, very hard to not kill someone in two. From a realism perspective, the problem is not that a high-level D&D fighter can survive a dozen sword cuts and spear thrusts but that he cannot die by any one attack.