Having now done this twice, what is it with me and grappling rules, and what principles are involved?
Coming to Grips
Grappling is probably one of the oldest forms of combat on the planet, is most often used by animals when hunting, and is something that both kids and animals (and animal kids) do for play.
And yet, the rules, by and large, suck.
Why is that?
The TV Tropes entry gets it both right and wrong. Grappling seems complex, and is often made so. It’s different enough from “hit him with my mace” or “boot to the head” that complex systems are often created.
That’s not required, though…
Use What’s There
The first rule of grappling is to use the rules you already have. I did this in Technical Grappling when I noted that a striking player will need to attack, the foe defends, and then if successful an effect roll of some sort is required to see what happens. Ideally, when it’s time to grapple, you should use the exact same mechanics.
Roll to hit: This may well be a different skill as striking or not. In GURPS, there are three unarmed striking skills, three unarmed grappling skills, and a metric crap-ton of weapon skills. You should not have to break out a new rules set to grapple. You should do the same things you always do.
When it came to OSR grappling in Gothridge Manor #8, Peter and I applied the same theory. In D&D, if you want to hit, you roll vs. Armor Class. Why should grappling be any different? So much gets swept under the rug in rolling to hit in D&D anyway, AC makes as good a proxy as a resistance to grappling as anything.
Oh, you don’t like that? Mail or scale armor doesn’t make you any harder to hit than leather for grappling? You might be right . . . but in the OSR, monsters usually don’t have stat blocks, so unless you want to do something like “roll against 10+ half the hit dice of the monster” then AC it must be. In other editions and versions where monsters get full stats? No problem: 10+DEX bonus.
Make it Interesting
Striking damage rolls are variable. So why not make grappling have a variable effect too? That was my solution for TG, and it makes total sense to use some dice-proxy for control as a measure of how good your grapple is. I think Peter and I found a good solution for the Manor, and the GURPS ST progression naturally supports control points for grappling in scale.
The thing about making it interesting is the key rule for these rules: grappling should be a useful device for combat. Grappling a relatively equal foe should neither be pointless or an “I win!” button. It should be something that when it happens is cool, and allows things that make the grapple worthwhile. It has to be as compelling in its place as bashing a guy with a sword or shooting him with an arrow in terms of fight-ending ability, without being a magical nuclear weapon (“I’ve got him in a tentacle lock! Demogorgon is so toast!”)
Reduce Book-keeping Where Possible
In most games, you already keep track of hit points, counting down from the max. For grappling, one nod to complexity is that you have to keep track of the total strength of the grapple for each combatant grabbed. The GURPS system uses penalties, but the D&D-based ones don’t have to, though they can.
What else can be done? What options are there, and pros and cons?
You’re easier to hit: Your AC could go down as you get grappled more. This is part and parcel with . . .
You’re clumsier and restrained: When trying to make attacks, the more grappled you are, the higher penalty you should take when swinging weapons and fists. Because you have to get even more up close and personal than usual (probably within the same 5′ square), having penalties to attack and other bonuses decrease rapidly is probably the right way to go.
You can’t move very well: D&D5 does this with the grappled condition already, restricting movement. As you get more and more grappled, it should be harder and harder to move in a direction you wish to go.
You’re open to injury and compelled movement: Being grappled invites the inevitable arm-bar type of motion. Techniques that translate restraint into actual injury. This gets back to putting injury points and control points on either the exact same scale, or some easily transferred quantity (two control points might be one injury point, or vice versa). As your foe gets you more under his control, he can also move you around.
The nice thing about using the same mechanics present in the “normal” combat rules is that nothing special needs to be done for counter-grappling. If you attack and roll to increase control, you can attack and roll to decrease it by trying to break a hold. You can also grab right back, making a useful choice with narrative power.
On One Condition
One thing present in versions of D&D but not quite so much in GURPS (or at least in a grappling-useful way) is the concept of Conditions. These descriptive phrases have game-mechanical weight. If you’re Prone, Grappled, Restrained, or Paralyzed (in D&D5), that means something very specific. It would be a trivial thing to borrow these conditions directly upon reaching certain control point thresholds. In fact, this ties in directly with reducing book-keeping, since setting thresholds for Conditions based on accumulated control means is all the GM needs to worry about is what threshold is crossed, and the foe is impacted as appropriate.
Fighting bloodies your foe. Occasionally it might knock him down (that’s easier in GURPS, where the Sweep especially is a non-grapple way of knocking someone prone). But the thing about grappling is that it probably needs to open up the target to something kinda neat.
Injury has already been discussed, but frankly you’ll injure someone more with a sword, and faster, than with a grapple. That works.
But there are things you can do with grapples that are harder or impossible than with a strike. Disarms for one. Throws, for another. Crippling limbs is a great one where such effects are allowed in games. Applying pain that stops when the fighter decides it, rather than when the organs grow back, is a way to make some critters give up without killing them.
Grappling is for Monsters
Even more than the players, grappling needs to be seen as a useful tool for the GM to make the players’ lives a tetch more interesting than they’d generally like. Getting grabbed by a giant scorpion should make it easier to hit the grappled character. It should be scary. A well-crafted set of grappling rules will make for better stories, and will frankly make for more believable encounters. A crocodile is scary because of the bite, yeah, but it’s because they bit with three tons of force (or more) and then drag you underwater to drown. A lion bites the neck to suffocate its meal, not to make it bleed to death. Cats will strike with their claws, but they will also grapple, and then rake with the back claws. Perhaps ironically, bears don’t bear-hug, but snakes do.
In any case, mostly grappling is a great tool for the GM to make giant monsters fracking terrifying and something you don’t walk up to casually so you can start swatting at it with axes.