Yesterday I ran a game of my Alternate Star Wars campaign where the party was traversing a spaceport infested with rakghouls (fast, nasty, infectious space-zombies). I wanted to throw a lot of them at my players so I looked around at various “horde” rule offerings. They started in GURPS Horror and were expanded upon in GURPS Zombies, but over at gurpsshooting.blogspot.com there’s an interesting article on Tactical Swarms, where the author took the materials from Horror and Zombies and adapted them for his own needs in modern gunfighting combat. I liked it a lot and used some of it in my game.
At first, I threw four swarms of six rakghouls each at the party, so what would be a total of 24 individual combatants otherwise. Inspired by tactical swarms, I increased the swarms’ effective skill depending on the number of constituent units, but instead of a flat +1 per unit after the first, I used the SSRT. My initial feeling was to read the number of rakghouls in a pack as linear measurement and use the corresponding SM bonus, but seeing 2 individuals would’t get any bonus I increased the bonus from the table by 1. I also decided to read in-between values opposite as to how the SSRT usually works, using the lower instead of the higher breakpoint. With that, a full pack of 6 rakghouls or one with 5 got +3 to skill, which dwindled down to +2 at 3-4 and +1 at 2. I liked those numbers.
Also inspired by tactical swarms, I rolled vs HT for the rakghouls if a major wound was indicated, “killing off” a unit in the swarm on failure. I did the same without a roll if they suffered a reeling or worse injury. The primary reason for automatic elimination at a reeling injury was simplification – I didn’t want to bother with parts of the swarm getting slower than the rest, even if the rakghouls themselves were tough enough to continue fighting in such a state. I may reconsider this in the future, eliminating units in such, thematically speaking “resilient” swarms (maybe indicated by having High Pain Threshold) automatically only on a full-HP or worse wound. As for the reeling condition in such cases, I would either ignore it entirely for the sake of simplicity even though it would give the swarms an advantage, or maybe reduce Basic Move of the swarm by an eyeballed value for each reeling constituent, down to a minimum of 1/3. Reduction by 1 in 6-unit swarms seems fine, but mobs of 3 or even 2 units could get slower. I think I’d be fine with ignoring it, because swarms generally consist of relatively weak opponents anyway.
Now, both the tactical swarm and Horror/Zombies rules also track total swarm HP and “dissipate” it once it reaches a certain threshold, but I use Conditional Injury so that was one less statistic to keep track of. I could imagine running it like that even in games that otherwise don’t use it, just paying attention to individual major, reeling and full-HP injuries.
When it came time for my swarms to join the melee, the Horror/Zombie rules for making a single rapid-fire like attack per swarm with recoil 1 and RoF equal to the total number of attacks the swarm’s constituents would otherwise have worked quite well. I went with the victims defending as against separate attacks and not against a single rapid fire attack with multiple landed shots, because my initial impulse was “swarms are abstracted, player characters aren’t”. I learned after the fact that this is how Horror/Zombies does it as well, though I could still see it working the other way without causing problems.
Having swarms of 6 units proved very pleasing because 6 opponents can encircle and attack a single victim at reach 1 anyway. I did experiment a bit when it came to grappling however, because Basic indicates that at most 3 combatants can effectively grapple a single target. So I decided that the first 3 attacks that landed were grapples and the rest were strikes; this worked quite well. I use Fantastic Dungeon Grappling so I could repeat this even after the initial grapple was established, whereas it would likely have to be more complicated with the default grappling rules.
At a later point during the game, I attacked the party with a single 6-unit security droid swarm plus an individual much tougher droid. Combining all the security droids’ attacks into just one with a very high RoF worked out very well. I used the rapid fire skill bonus based on half the SSRT as (I believe) proposed by Douglas Cole, which threw a small wrench in my gears – I calculated the skill bonus due to swarm size according to the full SSRT bonus, but the rapid fire bonus equal to half that. This took a bit more cognitive effort than I’d like so I’ll be considering alternatives. If I went with the full SSRT bonus a squad of 6 shooters with rapid fire weapons could easily get +8 or more; I’m not really sure if that would be too much or not, so I’ll need to playtest it. Another alternative would be to take the greater of the swarm size bonus and a rapid fire bonus like this instead of adding them up.
And then… one of my players threw an ion grenade in the middle of the swarm. Anticipating situations such as this, I played around with swarm formations, or rather “packing densities”. A 6-unit swarm could occupy what’s usually called a 2-hex radius in GURPS, so a single empty hex and all of the hexes surrounding it. In case of smart adversaries they’ll likely want to spread out a bit to minimize area effect and explosive damage. So that’s how the droids were positioned, with 1 empty hex between each of them. I figured the average distance from the center of the grenade was 3 yards, applied the appropriate bonus to the resistance roll (effect similar to warbler/strobe from Ultra-Tech, but disables droids), and then looked up the Statistically Speaking table on GURPS Zombies page 113 to see what fraction of the swarm would resist. And lo, all but 2 droids in the swarm dropped in electric spasms! I think that having to open the PDF and find the table took me the same time as rolling for each droid would have, so I’ll be able to save some time here by putting that table in a convenient spot to look it up. I definitively recommend it for use in scenarios like these.
Getting back to packing densities and the area occupied by swarms, I’ve had success in changing those during swarm movement in situations where they had to squeeze through tight corridors or between obstacles. MapTool makes it very practical with four different predefined token sizes. And if you force a swarm to assume a tighter formation to get through a choke point, you’ll have a fine opportunity for more effective area attacks. I was also reducing the size of swarm tokens as their constituents were getting eliminated, which was very fun for my players. So that’s definitively something that’s interesting to play with for both tactical and illustrative purposes.
I haven’t tried swarms containing more than 6 units, but I think I’d tweak those slightly. Instead of making a single rapid fire attack, they could make multiple depending on their size, to spread the love among player characters. I could even see doing this for 4+ unit swarms if they intend to grapple; one attack would be performed by the 3 units grappling the target, and another by the rest striking it.
That’s it for now, I’m looking forward to further experimenting with this in my upcoming games. The rules presented in Horror, Zombies and Tactical Swarms are very good, especially if combined with Conditional Injury and Fantastic Dungeon Grappling. And facing players with screaming hordes of enemies was immensely fun.