Manipulating Terrain

Tuesday, March 15, 2011

For the last installment of the Design Tuesday blog on terrain, we are going to look at a relatively new type of terrain—terrain that you can actively manipulate. This kind of terrain can grant a creature a variety of effects, from an attack, to cover, to a special or enhanced mode of movement.

Some of the examples of this type of terrain will look familiar. Much of it can already be found within existing encounters. Where this is the case, it is up to you, the GM, to decide whether or not you wish to allow the special terrain effects described below.

Other samples of this type of terrain are new. Some, like the blink crystal, grant magical effects, and can add a sense of mystery and danger, as well as the possibility for strange tactics on the part of the PCs and their opponents.

Like the hazardous terrain presented last week, these new terrain types straddle the line between terrain and new dangers. Based on how much of this terrain you plan to use, you may want to consider adjusting the CR of encounters that use these more active forms of terrain, especially if their use grants one side of the combat more advantage than their foes.

Alchemical Devices: This terrain is actually a broad class of similarly acting terrains. They can be as simple as a workbench cluttered with beakers filled with roiling concoctions, or as complex as a distiller or even stranger alchemical machines. Manipulating such devices requires a standard action and any number of skill checks. Toppling a table requires a Strength check. Making a distiller shoot a gout of highly-pressurized alchemical gas may require a Disable Device check, a Craft (alchemy) check, or even a Strength check, if the PCs are using a strategic application of brute force. Interacting with more complex machinery usually requires a Disable Device check, though a higher DC Craft (alchemy) or Knowledge (arcana) check may do in a pinch.

Whatever the type of alchemical device, the basic rules for its manipulation are as follows. A successful check made as a standard action creates a 15-foot cone (or alternatively a 20-foot line) of damaging energy, controlled by the creature that successfully manipulated the device. It deals damage to creatures within the area of effect. A Reflex or a Fortitude DC halves the damage. Often alchemical devices create an area of acid, but the destructive energy could be cold, electrical, fire, or in rare cases even sonic or force damage, depending on the nature of the device.

To add more flavor and danger to specific alchemical devices, you can layer on additional conditions and effects. You could add bleed damage (which works well for acid or even fire damage devices), have creatures knocked prone on a failed saving throw (for sonic or force damage devices), or have a failed saving throw entangle creatures for 1d4 rounds (for cold damage devices) or even daze creatures for 1 round (for electrical damage devices).

The following are some suggestions for baseline effects of alchemical devices based on the base CR of the encounter.

Simple Alchemical Device (CR 1–5): Activating—DC 14 check; Effect—DC 12 Reflex saving throw for 2d6 acid, fire, or electrical damage, or a DC 12 Fortitude saving throw if the device deals cold, sonic, or force damage.

Complicated Alchemical Device (CR 6–10): Activating—DC 17 check; Effect—DC 15 Reflex saving throw for 3d6 acid, fire, or electrical damage, or a DC 15 Fortitude saving throw if the device deals cold, sonic, or force damage.

Advanced Alchemical Device (CR 11–15): Activating—DC 22 check; Effect—DC 20 Reflex saving throw for 4d6 acid, fire, or electrical damage, or a DC 20 Fortitude saving throw if the device deals cold, sonic, or force damage.

Magic-Infused Alchemical Device (CR 16+): Activating—DC 27 check; Effect—DC 25 Reflex saving throw for 4d6 acid, fire, or electrical damage, or a DC 25 Fortitude saving throw if the device deals cold, sonic, or force damage.

Blink Crystal: These strange, cloudy-white crystals glow with a faint purplish radiance. Typically blink crystals are the size of large gemstones, and they are always set in a statue or some similar large and immobile casing. If a blink crystal is removed from its casing, it loses its magic and becomes nothing more than a large piece of common quartz (worth 10 gp). A creature adjacent to a blink crystal can touch it as a free action, which causes the creature to teleport up to 20 feet to an unoccupied space on stable ground within line of sight. Touching a blink crystal as a swift action along with a successful DC 20 Spellcraft or Use Magical Device check can increase the range of the teleport to 40 feet. Failing this check allows the creature to teleport 20 feet.

Bubbling Caldron: A size Large bubbling caldron can be tipped over with a DC 15 Strength check made as a standard action. Doing so releases a 30-foot cone of boiling liquid from the caldron in the direction of the creature’s choosing, and deals 2d6 fire damage to all creatures within the cone’s area. A successful DC 12 Reflex saving throw halves the damage.

The liquid makes the area of the cone slippery (Pathfinder RPG Core Rulebook 412) until it dries or dissipates. The cone of liquid affects creatures on the ground only. Flying or levitating creatures can avoid the liquid and its damaging effect.

Chandelier: Successfully leaping onto a chandelier allows a creature to hang from it and use its momentum to increase the power of a jump before the end of the leaping creature’s next turn. A creature is flat-footed while it hangs or balances on chandelier.

Using the momentum of the chandelier grants the leaping creature a +5 circumstance bonus on Acrobatic checks made to jump off the chandelier, and the jump is considered to have a running start for purposes of determining the DC of the check.

Chandeliers have size categories like creatures do. They are typically size Small or larger. A chandelier can easily support a single creature of its own size or smaller.

A creature larger than the chandelier’s size (or two creatures of the same size or smaller than the chandelier) can attempt to hang on it or use it to gain the bonus on Acrobatics checks made to jump, but at the end of the creature’s turn (or the second creature’s turn, if two creatures are using the chandelier for the same effect), the chandelier breaks free from its supports and both the chandelier and any creatures hanging from it fall to the ground. If either a creature two or more size categories larger than the chandelier or three smaller creatures leap on to the chandelier, the chandelier and those hanging on it fall immediately. Creatures take normal damage from the fall plus an additional 1d10 damage from the falling chandelier. At the GM’s discretion, extremely large or heavy chandeliers or chandeliers with sharp protrusions or other dangers can deal additional damage upon a fall.

Furniture: From flipping over a table to using a gong as makeshift shield, a movable piece of furniture can be manipulated to create partial cover for a short period of time. A creature that is adjacent to the piece of movable furniture can attempt a Strength check as a move-equivalent action to gain cover from the item until the start of its next turn.

The DC of the Strength check depends on the size of the furniture. The base is DC 10 for size Small furniture, and the DC increases by 5 for each size category over Small (moving a Medium piece of furniture is DC 15, moving a Large piece of furniture is DC 20, and so on). A creature cannot attempt this manipulation if it is two or more size categories smaller than the piece of movable furniture it wants to manipulate.

Rug: A creature can spend a standard action to attempt to pull a rug out from under creatures standing atop the rug. This requires a DC 15 or higher Strength check, depending on the size of the rug. If successful, each creature standing atop the rug (some of its space must be on atop the rug) must succeed on a DC 12 Reflex saving throw or fall prone. Creatures that cannot be tripped are immune to this effect. Rugs that are larger than a 4-square area require higher Strength checks. The DC increases by 2 for every additional 2 squares of rug area beyond 4 squares.

Stephen Radney-MacFarland
Pathfinder RPG Designer

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Liberty's Edge RPG Superstar 2011 Top 32

Really useful article. I used terrain to great effect when I played 4E and now I can use the same principles easily in Pathfinder. I'll have to stat up a tipping wall as well, which was one of my favorites although the alchemical bench may be even better. The bubbling cauldron also goes great with fights against witches and hags. Thanks, Stephen.

RPG Superstar 2010 Top 16, 2011 Top 32, 2012 Top 4

I especially liked the chandelier rules. I could see applying those rules to jungle vine swinging as well. I may have to introduce that to my Serpent Skull campaign.

Nice work!

Scarab Sages

Very nice blog! I always like to reward players who try to lean their characters into the cinematic, and this is a nice set of ideas. Thanks!


Pathfinder Adventure Path Subscriber

I like it, but I think the Rug is too easy. If there are multiple opponents on the rug, I think the DC should be higher (+2 per creature above 1).

Otherwise, good article!

Grand Lodge

Pathfinder Adventure Path, Companion, Rulebook Subscriber

Those Blink Crystals are an awesome device for setting up defense in your evil lair (tm).

By placing them say, at the side of your throne, your henchmen and lieutenant can quickly leap from your side, to your foes flank, making your once confident enemy suddenly surrounded.

Of course all lair thrones these days should also come equip with a button that activates a create pit spell.

The Exchange

1 person marked this as a favorite.

Added to d20pfsrd.com Hazards/Terrains section.

Liberty's Edge RPG Superstar 2008 Top 32, 2011 Top 16

I like the ideas on some of these, but not sure about the implementation. For example, why even a DC 10 Strength check to pull the rug out, and then allow a saving throw? Pathfinder already has rules for tripping, so shouldn't using the rug to trip use the CMB rules and provide a bonus if the character makes a Str check? Even a strong character - Str 18, won't make the strength check 25% of the time.

The same thing applies for furniture as cover - those Str checks seem awfully high for furniture that a strong character could probably just lift based on carrying capacity.

For the alchemical devices, the CRs look very high for the effects the produce. CR 16+ for 4d6 damage? As terrain and not traps, I am not sure if a CR is even appropriate.


I like the ideas being presented here, but I don't think the right approach is to create a bunch of different kinds of terrain and then assign DCs and saving throws and other mechanics to each one. This approach tends to make people focus on individual mechanics when the real goal should be to get Game Masters to think about terrain itself as interactive, and give them guidelines about how to incorporate interactive terrain into their encounters with general advice and guidelines so that GMs are encouraged to come up with their own ideas.

Here are ten, off-the-top-of-my-head examples of how a character could incorporate active terrain into their actions:

1. Throwing dirt into someone's face.
2. Rolling a boulder down a hill.
3. Yanking a chain attached to a wall.
4. Scooping a handful of coals from a fire onto someone.
5. Throwing a lit oil lamp on someone.
6. Using a pot lid as a makeshift shield.
7. Dumping a bucket of soapy water on the floor.
8. Tipping a bookshelf onto someone.
9. Slamming a door into someone's face.
10. Tangling someone up in a bedsheet.

The potential uses of terrain are quite literally infinite. But nobody is ever going to come up with mechanics for all of them. A GM simply needs to know some guidelines about adjudicating these actions and providing a way for the attempt to be ruled successful or unsuccessful.

GMs have been doing this for years. Here is how I would rule on each of these if a character attempted these actions (or if an NPC did):

1. If you are prone or crawling on a dirt floor, grabbing a handful of dirt is a free action. Otherwise it's a move action that provokes an attack of opportunity. Throwing it in the face is a ranged touch attack that blinds the opponent for 1d3 rounds unless they make a reflex save, in which case it does nothing (the target successfully closes their eyes and avoids the dirt).
2. This is a str check with conditional modifiers based on the boulder's size, position and orientation. A successful check means the boulder rolls down the hill on a straight line. Any creature within the path makes a reflex save or gets hit by the boulder for 1/2 the damage they would receive from falling the same distance the boulder has traveled.

etc...

Anyone can make these things up, and the goal should be to encourage GMs (and players) to view terrain items as interactive game components and to be creative about exploiting them in encounters, or even in non-combat situations.


Pathfinder Rulebook Subscriber

I agree with brassbaboon. I'd like to see next week's blog be about more general guidelines instead of just specific examples. And I'd like to add that I'm interested in destructible terrain, like crates in a warehouse being used for cover. I know how to damage objects, that part is easy. What I'd like is advice on how to track it, when a miss should count as hitting the terrain, that kind of thing, without it becoming a massive chore.

Liberty's Edge RPG Superstar 2011 Top 32

Talynonyx wrote:
I agree with brassbaboon. I'd like to see next week's blog be about more general guidelines instead of just specific examples.

This blog was the third of three. The first blog had general guidelines and this third one has specific examples.

Dark Archive

I thought of something like this before in an encounter where the PCs encounter a ghost that moves freely around book shelves in a library. The PC fights the ghost but have to navigate around the shelves when the ghost does not. The PC's can knock over the shelves making the area rough terrain with a chance of losing balance over the books


Charles Dunwoody wrote:
Talynonyx wrote:
I agree with brassbaboon. I'd like to see next week's blog be about more general guidelines instead of just specific examples.
This blog was the third of three. The first blog had general guidelines and this third one has specific examples.

I did go look at the two previous blog entries on terrain. They were not in the same vein, they were about creating terrain that players move around on or in. Examples used were fighting on a frozen lake, or dealing with a building on fire, or razor-sharp rocks...

This was the only blog entry I saw that dealt with physically utilizing terrain elements as part of the encounter. The other blog articles seemed mostly to be about how to design and manage terrain movement and environmental effects.

Also good things to discuss, but not the same as this blog entry, not to my interpretation anyway.


I'd say the first one also generally covers the manipulation of terrain, however I agree that it was more overview then guidelines.

If you want to run out and generate your own set I suggest looking a few places. First is the "Page 42 for Pathfinder", nice breakdown of DCs by target CR.
http://gneech.com/rpg/page-42-for-pathfinder-revisited/

Second I notice Stephen using similar rules for traps when it comes to damage and spell effects. What's missing from a more genetic "terrain" list are movement, 'buffs', and a few other indirect things like creation of covet and smoke.

Really, I think what one can say is that the most useful tool would be getting various existing rules collected in one place to support quick look-up for "dynamic" terrain. Which is really what were talking about here.

Dark Archive

Love the cauldron!

The chandelair, rug, etc. were also cool.

Great little article!


Charles Dunwoody wrote:
This blog was the third of three. The first blog had general guidelines and this third one has specific examples.

I think for multi-part Blogs (which often have intervening material), having a ?jump list? saying ?See Part 1, Part 2...? would be most helpful.

Honestly, besides the fact that some of the quality can be spotty (see above complaints about crunch), I really think the focus should be on issuing Errata and FAQs. There?s really tons of stuff that could be dealt with.

I?d also like to know how long is the list of items that ?can?t? be Errata?d because of the ?preserving page number reference? issue. I don?t know, maybe it?s only 1 or 2 items. Maybe it?s 50 items. Or more. I don?t know if the ?preserving page number reference? rule might be revisited depending on the number (or total importance of) this list of ?can?t do? Errata, but it seems like something reasonable to take a look at instead of ignoring it. At the least, these are things that Paizo would definitely want to address in a ?new version?, which could include the ?Entry Level Rule-Set?.

I also think that moving away from the ?Errata is only issued on re-print? would be more efficient... There?s no reason it can?t be issued on an on-going basis, and of course still rolled into the latest printing whenever a new one goes out. It just seems like a better way to actually get Errata dealt with, rather than leaving it to the last second and probably not get all of it. You guys seem to have problems accurately scheduling what can be done in a fixed time period, and with all the other time demands you have it seems like Errata is skimped on. Actually scheduling on-going work on it seems much more likely to see solid results.

Also, has Paizo gone thru all the Errata reported to the Errata thread BEFORE the flag system was implemented?


Pathfinder Rulebook Subscriber
brassbaboon wrote:


1. If you are prone or crawling on a dirt floor, grabbing a handful of dirt is a free action. Otherwise it's a move action that provokes an attack of opportunity. Throwing it in the face is a ranged touch attack that blinds the opponent for 1d3 rounds unless they make a reflex save, in which case it does nothing (the target successfully closes their eyes and avoids the dirt).

That would be a Dirty Trick combat maneuver.


Pathfinder Adventure Path, Companion, Lost Omens, Rulebook, Starfinder Adventure Path, Starfinder Roleplaying Game Subscriber

I wouldn't bother asking anything having to do with faq* or errata* at this point.


Cool! Now make 'em scale on-the-fly and we'll be good to go. ;)

-The Gneech

Dark Archive

Good stuff here sir. Good stuff.

Dark Archive

tdewitt274 wrote:

I like it, but I think the Rug is too easy. If there are multiple opponents on the rug, I think the DC should be higher (+2 per creature above 1).

Otherwise, good article!

I think utilizing the rug shouldn't be a strength check vs. reflex save; rather, it looks like a standard CMB check. As CMD already includes the opponent's dexterity modifier, so there's no need for a reflex save.

That minor gripe aside, I like it a lot! Well done, Stephen! :)

The Exchange

Casts Raise Thread...

Finally reading through this (whilst pretending to be busy at work)... I think the fact these are Strength checks and Reflex saves and the like makes sense, basically because the CMB / CMD thing already has a bunch of potential modifiers which could make these object-based options look a bit wonky. E.g. if these were CMB-based my Str 3 / Dex 20 Wizard with the Agile Manuevers Feat could flip heavy tables and pull rugs out from under people with the best of them!

As for the Strength check DCs being high I don't think it's really a question of whether you could, ultimatly, flip that table or not (that's carrying capacity, or taking 20), but rather whether you can quickly flip it in a burst of strength during combat.

The one thing I find a bit weird is that flipping a table covered in alchemy stuff is a Standard action, but flipping a table covered in anything else is a Move action...

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