After a big ol' discussion on the OSR Discord about a campaign all about descending down a massive overhanging cliff face (this cliff is several thousand miles long), I am going to write a bunch of rules for various climbing and mountaineering related things. I am going to be assuming some level of climbing technology, so it's definitely going to be anachronistic for any game set before the 1930s or so. Mostly, I'll try to assume 1960s levels of competence and technology (such major climbs as the first aid climb of El Capitan and the first free climb of a 5.10d happened in the late 50s).
Gear
There's a lot of climbing gear and jargon so I'm going to make a list of a lot of it here with definitions. "Slots" refers to the GLOG inventory slots.
Anchor: An anchor is what you fix your ropes to at the top of something. Typically, it's a couple of pieces of protection (see below) or a solid natural feature such as a large rock you can loop your rope around, something strong wedged in a crack, or a solid well-rooted tree. A typical anchor (not using a solid natural feature) requires 3 pieces of protection and 10 feet of webbing or cordelette (see below).
Belay: Belaying is controlling a rope that someone is climbing on the other end of so that they can climb without the rope hindering them but have the rope hold them when they fall. Since top-rope belaying isn't relevant to RPGs, being a purely recreational activity, this refers only to
lead belaying and
belaying from above.
Belay Anchor: A belay anchor is what the belayer (the person belaying the climber) anchors them self to so that they don't go flying off somewhere if their climber falls and yanks them, or if a rock hits them in the head (wear your goddamn helmet), or any other unforeseen occurence would move you from where you need to be to belay. Constructed the same as a regular anchor (above).
Belay/Rappel Device: A belay device is the equipment you use to regulate the rope while belaying so that you can actually take the force of a fall, rather than the rope ripping itself from your hands. You can belay without equipment using a hip belay, but it isn't recommended. A belay device can be just a simple carabiner (using the Münter hitch), but there are a variety. All belay devices can also be used for single-rope rappelling (see below), and most can be used for double-rope rappelling. For our purposes, all belay devices are 1/3rd of a slot and can be used for belaying, single-rope rappelling, and double-rope rappelling.
Bolt: A bolt is a solid and permanent piece of protection (see
below) drilled into the rock. It doesn't require any natural features to
use, but to place one you must have a drill. As gear, 1 bolt takes up
1/10th of a slot.
Carabiner: A carabiner is a loop of steel with a gate. Many have locking gates. They are unspeakably important for anchors and many other climbing applications. If you are equipped for climbing, assume you have infinite carabiners because fuck keeping track of anchor construction in detail.
Climbing Shoes: Climbing shoes are specialized shoes with high-friction rubber on the bottom. If you're equipped for climbing, you have a pair, and you
need them to climb difficult routes. If you're carrying them, a pair of climbing shoes is 1 slot.
Cordelette: Cordelette is a relatively thin but strong static cord (see static rope below) often used for constructing anchors. 10 feet (enough for an anchor) is 1/3rd of a slot.
Crampons: Crampons are spikes that you attach to your boots in order to ice climb or walk ice of more than moderate steepness (in combination with an ice axe to cut steps). If you're carrying them, a pair of crampons is 1/3rd of a slot.
Harness: A harness is both what you wear to keep yourself attached to your rope, belay device, anchors, etc, and where you attach all your climbing gear. For our purposes, all harnesses include a personal anchor system (how you attach yourself to an anchor so you can do stuff with the rope you're tied to without falling), and do not take up any slots. In fact, they count as a belt for quick-access slots.
Ice Axe: An ice axe is a shaft with a point on one end and a head consisting of a pick and an adze (or hammer) on the other end. Longer ice axes are mostly used as walking sticks on ice and for keeping yourself from sliding precipitously down an ice slope. The adze is mostly used for cutting steps in ice. An ice axe is a light melee weapon, but isn't throwable and takes a full slot.
Ice Tool: An ice tool is a small ice axe required for ice climbing (typically, 2 are used for ice climbing). They typically have a hammer rather than an adze. One ice tool takes 1/3rd of a slot.
Ice Screw: An ice screw is a piece of protection (see below) that can be screwed into solid pieces of ice. They are reusable (like cams), and 1 ice screw is 1/10th of a slot.
Mechanical Ascender: A mechanical ascender is a small device that allows you to ascend fixed ropes. It grips the rope solidly unless "opened" in order to move it along the rope or take it off the rope. A mechanical ascender does not take up any slots, and you need at least two to climb a rope.
Pitch: A pitch is a section of a long climb that must be split up into portions (for rope length or many other reasons). A pitch must have an appropriate spot for anchoring and belaying on either end.
Piton: A piton is a piece of protection (see below). It is a small metal spike or shim which can be hammered into cracks in the rock. 1 piton takes 1/10th of a slot, and using pitons requires a hammer or an ice tool (1/3rd of a slot). Unlike ice screws and sustainable protection (see below), pitons can only be successfully removed from the rock 50% of the time.
Protection: Protection is the term for things you put into the rock or ice and then attach to the rope so that if you fall, your fall will be arrested by the protection, or in order to create an anchor. Protection pieces also need slings of webbing (see below) and carabiners to attach them to the ropes, but we're assuming that those are included with the pieces of protection so you don't have to keep track of them.
Prusik Knot: A Prusik knot (or one of the many, many variations on it) is a knot used to tie a piece of cord or webbing around a rope so that the rope can be ascended, or as a "third hand" while rappelling (don't worry about this; it's assumed you have one). A Prusik knot does not take any slots.
Rappel: Rappelling is the process of descending a face by ropes hanging from an anchor on the top of the face. It can be done with a single rope or a doubled-up rope, and there's a lot more detail in the section on rappelling in Types of Climbing below.
Rope (Dynamic): Dynamic ropes are ropes which stretch under high forces in order to lessen the force of a fall. They are mostly used for free climbing (see Types of Climbing below). They can be used to rappel, but this can cause bouncing and put undue stress on the anchor. Modern dynamic ropes can get up to 80 meters long, but we'll assume that all dynamic ropes are 200 feet long and take 1 slot. Climbing with a rope tied to you (such as lead climbing) takes 1/3rd of a slot.
Rope (Static): Static ropes are ropes which do not stretch under high forces. They are lighter than dynamic ropes and are better for rappelling, but should not be used for free climbing (see Types of Climbing below) unless there is no other option. A static rope is 250 feet long and takes 1 slot. Climbing with a rope tied to you takes 1/3rd of a slot.
Sustainable Protection: Sustainable protection refers to a number of various types of pieces of protection which, unlike pitons, can be easily removed from the rock (usually) and don't cause damage to the rock (although that's unlikely to be something you're concerned about). The most common types are cams and nuts. 1 piece of sustainable protection takes 1/3rd of a slot.
Webbing: Webbing is a strong flat strip of fabric used similarly to ropes. It is static and often used when constructing anchors. 10 ft (enough for an anchor) is 1/3rd of a slot.
Yosemite Decimal System: The Yosemite Decimal System is the American system for ranking climbs by difficulty. Technically, it can be used to rank any trail, hike, or climb (Class 1 is walking, 2 is terrain where you may occasionally have to use your hands, 3 is scrambling, 4 is a very exposed scramble, and 5 is technical climbing), but the part we're concerned with is the subdivisions of Class 5. They go from 5.0 on up. 5.0 - 5.5 is trivial as far as technical climbing goes, 5.6-5.9 is easy for people with some experience, and 5.10 on up is where things begin to get difficult. From 5.10 up, each grade is further subdivided into a, b, c, and d, with a being an easy climb for that grade and d being a hard climb for that grade. The highest-rated climb ever free-climbed (see below) is a 5.15d. For reference, the highest grade I have ever free-climbed as a mediocre but modestly experienced climber is a 5.10d. This rating system is only for rock climbing, not ice climbing, but we're going to use it for ice too because I don't ice climb and ice rating systems are confusing.
Types of Climbing
I'm going to restrict these rules to five types of getting where you're going, with both ice and rock climbing included. The types are aid climbing, free climbing, free soloing, rappelling, and climbing along fixed lines. Rappelling isn't strictly a type of climbing, but it's incredibly important, so we'll talk about it too. There's a couple of things I'm leaving out that
could be relevant, like simulclimbing, but fuck it.
Aid Climbing
Aid climbing is using equipment to help you get up/down the face. Vital gear is pitons or bolts, to secure your stuff and yourself to the cliff. You have stuff like etrier (rope ladders), fixed lines, belay/rappel devices, pulleys, and Prusik knots or mechanical ascenders to help you and your stuff get up and down. Aid climbing is slow but safe and, given a willingness to drill many holes, pretty much infallible. It can be done solo or in teams of two to three.
Free Climbing
Free climbing is climbing with at least one partner (we'll say no more than two partners for our purposes) and using protection in the rock to keep yourself safe but not relying on that protection to climb. You climb on the rock, but have a rope fixed to the rock so if you fall it will hopefully not kill you. It's much faster than aid climbing but carries significantly more risk.
Free Solo
Free solo climbing is climbing by yourself with nothing but you and the rock. It's the fastest way to climb, but if you slip that is it and you are dead. Not too much more to say about it; it's very simple and very dangerous.
Rappelling
Rappelling is the main descent tool in a climber's toolkit. You fix ropes at the top, then descend those ropes. As long as your anchor at the top is solid, it's pretty much infallible. The problem arises when you're on an overhang and your rope isn't long enough to get to the bottom (if there is a bottom), because you go straight down and the wall goes away from you. Your solutions are either to downclimb (which is hard and awful) or, if the overhang isn't too steep, to rappel a short distance, swing in to the wall, and hope there's something to catch hold of so you don't swing away again. If you can't swing in, you'll have to climb back up your anchor with Prusik knots or mechanical ascenders. There are two types of rappelling - single-rope and double-rope. Single-rope rappelling means fixing one end of your rope at the top of the wall, meaning that you can use the full length of the rope but the rope is stuck there unless someone is still at the top to untie it. Double-rope rappelling means that your rope length is halved, but that you can pull the rope through the anchor once you're at the bottom. You can tie ropes together, but you can only tie two ropes together for double-rope rappels because you can't pull the knot through the anchor.
Fixed Lines
If there's a particularly difficult pitch you're going to need to travel over a lot, or any pitch at all you need to get non-climbers or heavy gear across, you'll want to use fixed lines. You can anchor ropes along a traverse or up and down a vertical climb. People can then attach themselves to these ropes using Prusik knots (or any of the many variants) or mechanical ascenders. Just a simple carabiner will work for easy traverses. You then climb along the traverse, do
this along the vertical rope to get up, or rappel down along the vertical rope to get down.
The Rules
Now that I've gotten all the preamble out of the way and hopefully now that those who don't climb can understand a word I'm saying, here are the actual rules. They're loosely based around the GLOG (no specific hack) but they should be usable with adaptation for any given system.
The Climb Rolls
The mechanic I'm going to base this off is a modified d20 roll over a DC. You have two modifiers - your Climbing modifier and your Climbing Skill modifier. The climbing modifier is either your Strength mod or your Dexterity modifier, whichever is
lower*, plus an additional +5 if you're a very experienced climber, or a +3 if you have some climbing experience. This is used for the actual physical acts of climbing. Your Climbing Skill modifier is either your Intelligence or Wisdom modifier, whichever is
higher, plus an additional +5 if you're a very experienced climber, or a +3 if you have some climbing experience. This is used for the many technical skills associated with climbing, such as anchor construction and belaying.
*I have this mechanic as it is because both Strength and Dexterity, in D&D terms, are extremely important in climbing, and you will be limited by whichever you are worse in.
What is This Climb Like?
This section should hopefully help DM's determine how difficult a climb is. We'll use 2 numbers: D, for Difficulty of Climb, and P, for Difficulty of Protection. Difficulty of Climb is pretty straightforwards. A 5.0 climb, on the Yosemite Decimal System, is 1D, and a 5.15 climb is 16D. Difficulty of Protection refers to how easy it is to place protection on a route. Basically, any type of protection, excepting a bolt, can only be placed in a crack in the rock. Some routes, even if they have hand and footholds, don't have cracks next to where the climber can go and easily protect themselves. The P of a climb can be between 1 and 10, although it can't be higher than the D of a climb.
How Do You Determine Difficulty?
As the DM, how do you determine the D and P of a climb? My recommendation is to roll a d20 for D, with over 16 being truly impossible. You can also apply some modifiers to this roll based on what the cliff is like. An overhang might get a +2, a roof (severe overhang) might get a +4, a slabby (less than 90 degrees) climb might get a -1. An overhang is also unlikely to be less than a 5.9, aka 10D, and a roof is unlikely to be less than a 5.12 (13D). You can then roll a d10 for P, rerolling if it's more than D. You could add modifiers to this based on rock type, but I won't bore you with that.
How Do I Climb That Thing?
Ok, say your player wants to climb that cliff over there. First things first, if the character has some climbing experience, they don't need to roll to climb anything with 6D or below (5.5 or below), unless there's some circumstance making the climb harder. Very experienced climbers don't need to roll for anything 10D or below (5.9 or below), unless there's some circumstance making the climb harder. Circumstances that might make the climb harder is anything on the Circumstances table below and free soloing a climb. No matter how trivial the climb is, you always roll when you free solo. Now, if you do need to roll for the climb, you determine your DC. The base DC is 5 + D, and there might be some modifiers to that, in the below table (modifiers are specified for either rock climbing or ice climbing). If you roll over or equal to the DC with d20 + your Climbing modifier, you succeed. If not, you fail. There are different consequences to failure with different types of climbing, but success means you reach the top of the pitch.
| Circumstance |
Modifier |
| Crumbling (Rock) |
+2 |
| Wet (Rock) |
+2 |
| Icy (Rock) |
+4 |
| Fragile (Ice) |
+2 |
| Melting (Ice) |
+2 |
| Rotten (Ice) |
+3 |
| Carrying more than 3 slots of gear (Either) |
+1 per slot over 3 |
| Exposed (Either) |
+1 |
| Downclimbing (Either) |
+3 |
| You've attempted it before (Either) |
-1 per attempt |
Consequences for Failure
Aid Climbing
If you fail while aid climbing, the climber with the highest Climbing Skill modifier must roll Climbing Skill vs DC 6. On a failure, go to the consequences for lead climbing (in free climbing), but automatically succeed that Climbing Skill check. You messed up somehow and someone's fallen. On a success, you haven't made any progress in however much time it would have taken you to finish the climb on a success. You've stalled out wherever you started, and haven't gotten any further.
Free Climbing
The first person to free climb the route is lead climbing, any who follow them up while the first climber is belaying from above are toproping. If you fail while lead climbing, whichever of you or your belayer has the higher Climbing Skill modifier must roll Climbing Skill vs DC 6. On a failure, you messed something up and actually fell without the rope catching you. Go to consequences for free soloing. On a success, take Pd4 - P damage from shock and the rope catching you. If you're using static rope instead of dynamic rope, take Pd6 damage because that rope is not going to be gentle to you. Either way, you're back at the bottom of the climb, and as much time has passed as it would have if you'd succeeded the climb.
If you're toproping and fail, go to consequences as aid climbing.
Free Soloing
If you fail while free soloing, roll 1d4 to determine how high you were on the pitch before you fell. 1 is 25% of the way, and 4 is on the final move. Take fall damage corresponding to how far you fell. You're back at the bottom of the climb (or quite likely, your corpse is), and as much time has passed as if you had succeeded the climb.
Rappelling and Fixed Lines
You don't have to roll for rappelling or using fixed lines. However, if you put unusual stress on the lines (an extremely heavy load, for example) or the anchor is iffy for some reason, the person who constructed the anchor must roll Climbing Skill vs DC 8. On a failure, anything on the line suffers from consequences as if free soloing as the line pulls free from the anchor or snaps.
Rappelling on Overhangs
If you're rappelling on an overhang of less than 120 degrees from horizontal and you can't reach the bottom (don't worry, you won't slide off the rope, you tied a knot on the end), you must roll Climbing vs DC 15. On a success, you swing yourself to the wall and grab hold of it. On a failure, you can't get to the wall. Your options are to get the people above you to lower another rope down to you and keep rappelling or to ascend the rope as a fixed line.
How Fast Can You Do It?
| Task |
Speed |
| Aid climbing |
10 feet per minute |
| Free climbing |
20 feet per minute |
| Free soloing |
20 feet per minute |
| Rappelling |
100 feet per minute |
| Ascending a fixed line |
10 feet per minute |
| Traversing a fixed line |
30 feet per minute |
| Setting an anchor |
10 minutes |
| Setting a belay anchor |
10 minutes |
How Much Gear Does It Take?
| Task |
Gear |
| Aid climbing |
1 protection per 5 feet* |
| Free climbing |
1/P protection per 5 feet |
| Free soloing |
- |
| Rappelling |
Anchor at the top |
| Vertical fixed line |
Anchor at the top |
| Horizontal fixed line |
Anchor at either end, 1 protection per 10 feet* |
| Setting an anchor |
3 protection or a solid natural feature |
| Setting a belay anchor |
3 protection or a solid natural anchor |
*Aid climbing can only use 1/P pitons or sustainable protection per 5 feet, all other protection must be bolts, which require a drill to use. Horizontal fixed lines are the same, but per 10 feet.
In Conclusion
These rules haven't been playtested; take them with a grain of salt, or maybe several shakers worth of salt. Any feedback is appreciated and I'd love to hear if anybody uses them.
