One thing about poisons in games - and GURPS is one of those - it's generally not as scary as in reality. Pass a resistance check and you're okay. Deadliness varies, and although not all of them have resistance rolls (basically, not save or die, just . . . die) they generally do, and you usually get HT rolls not to die even after all of this.
So what if you want poisons to be a bit more systematically deadlier in GURPS?
First, don't forget the . . .
Rules As Written
Know your poisoning rules.
- Not all poisons have a resistance roll. Don't drink cyanide (B439).
- Some have HT roll penalties upwards of around -6 - don't get hit with curare (Low-Tech, p. 129).
- poisons often have multiple effects, such as damage and paralysis, or damage and a secondary chance of a heart attack, etc.
- Doubling a dose gives a penalty to resist and increased damage and reduced cycle times, per B439, Varying the Dosage, but makes it (much) easier to detect.
GURPS Dungeon Fantasy 2: Dungeons has a Practical Poisoning rule for when you want to double or quadruple venom doses for maximum effect - based on that same rule from Basic Set.
- Positive Size Modifiers delay poisons. They don't actually increase the needed dose, but they slow down the rate of the cycles. It takes longer to get to your heart, I'd guess. Negative size modifiers make them work faster!
- Persistent poisons hit you over and over while you're in the area, regardless of your success on resistance rolls. Lesson #1: When mustard gas comes in, you should go out.
- Delivery agents aren't always about skin contact or skin penetration. Don't forget sprayed venoms (usually Blood Agents or Contact Agents), Respiratory Agents, or sense-based (horrid smells, eye irritants, etc.).
But what if that's just not enough? Here are three ways you can make poisons deadlier, or at least more worrisome.
#1) Secret Resistance You can change how you run them, simply by not telling people the results of checks. Roll them secretly and just describe what happens. They'll have to assume the worst because they don't know if they made it or not. After all, "You take 3 damage" can mean a successful HT roll against a strong poison, or just a lucky damage roll.
This makes poisoning a bit more of a concern, but not actually deadlier. If anything, it might make it safer, but more expensive - not knowing if you've resisted or not, if you've taken the incidental damage of a successful roll or just got lucky on the effects of a failure, might drive you to use antivenins or magical cures in a fantasy game.
#2: Resisting Doesn't End Cycles - This is a big change. Right now, you make a resistance roll every time a poison comes up with a chance to affect you. If you resist, the attack ends and all further cycles are nullified.
I'm not a big fan of how this makes poison a lot less scary - all it takes is one good roll (or one of three, with Luck) to end its effects. Cobra bites you, you roll an hour later and resist and that's that. It has a tendency to make non-penalized HT rolls to resist poison not so scary. Most PCs get 12+ in this area, 14-15 or so with Fit, Very Fit, and so on, and may even stack Resistant to Poison on top. They normally resist right away, and if not, it's rarely more than 1-2 cycles before they do.
Changing it so you always apply all cycles, and must resist each as if it is was a new attack all over again, makes poison much scarier. Keep some antivenin around, because even a good HT roll early on only means you've bought some time to get help. It makes poison less "cobra bit me, make a roll and I'm okay" and more "cobra bit me, I'm going to suffer even if it doesn't kill me." This should affect the cost of Resistible, since part of the cost assumes success breaks the cycle of damage.
This will also make the more dangerous venoms (curare, cobra venom, nerve gas, fugu toxin) extremely dangerous, because even the rare success you get won't end it.
Optionally, you can make this an enhancement to certain venoms - persistant cycles. Cosmic is probably the way to do this, and the fairest cost wise.
#3: Multiple Hits Are Multiple Doses - This one might in fact be what the rules sort-of intend. Treat every single dose of venom as part of a unified whole, not separate attacks. So if you get stabbed with Caustic Tar with 4 doses at once, you resist at HT-4 or take 8 damage. If you get hit 4 times in the same second with 1 dose at a time, you roll at HT-4 or take 8 damage. Bit by a snake with HT-3, 2d, 1 hour onset and 6 cycles venom? At one hour roll HT-3. Bit three times? That's more than 2 but less than four, so it's HT-5, 4d, 30 minutes onset for 6 cycles. Suddenly, a pit full of spiders with weak (HT+4 to resist) poison isn't a trivial series of rolls, but a cumulative buildup towards a series of terrible rolls.
Beyond a doubled dose, just follow the rules on p. B439 and simply extend it out - every doubling of the doses applies another -2 to the resistance roll and adds another iteration of damage.
Run correctly, poison can be deadly, but those three optional rules are ways to make it a bit worse for the victims.