Mike Mearls Games
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Creatures and Terrain
🕑 Added 2024-08-13 17:00:07 +0000 UTCI promised the wizard write up this week, but COVID knocked my schedule around a bit. Plus, I've been a bit obsessed with monsters. Did you know that hyenas eat their prey alive? That's creepy and something that is informing my gnoll design work.
Since my gnolls aren't done and I'm building a dungeon out of terrain tiles for my Tuesday night game, I want to talk about terrain today.
Terrain is an overlooked part of running 5e encounters. In my experience, it's easy to get caught up in trying to model a piece of terrain like an object in a physics engine. It can fill a few squares, block line of sight, and so on.
Meanwhile, difficult terrain has been in the game since 3e and is pretty simple. A square of difficult terrain costs double the movement to enter. That's easy to understand.
I prefer to think of the net effect I want terrain to have, then build rules that create the right effect. By going this route, I can create terrain that does what I want without jumping through the system's hoops. Like difficult terrain, I just create a tag and attach it to a square or object. Like these:
Slashing Terrain (X): A creature takes X slashing damage the first time it enters this square each round.
Unstable Terrain: The first time a creature enters unstable terrain on a turn, it must make a DC 15 Dexterity (Acrobatics) check or fall prone.
We can spice things up a bit by adding beginning and end of round effects.
Careening Boulder: At the start of each round, randomly determine the direction the boulder rolls. Any creature that can see the boulder knows the direction it will move. At the end of the round, it rolls 3d6 squares in that direction. If it enters a creature's space, that creature takes 3d6 bludgeoning damage and is knocked prone. If the boulder ends its movement in a creature's space, move that creature to the closest, free space it can occupy.
Thin Ice: At the end of each round, roll a d6 for each square of thin ice a creature occupies. On a 5+, the thin ice under that creature breaks and that square becomes frigid water.
Frigid Water: At the start of each round, creature takes 5 cold damage and halves its speed for that round if it is in a square of frigid water.
Note the lack of a save on these effect. The "saving throw" in this case comes down to moving out of the boulder's way or avoiding areas of thin ice before the end of the round.
Natural 1 Terrain
I've also had fun with terrain where stuff happens on a natural 1, like this.
Spore Burst: Each time a creature in this terrain rolls a natural 1 on an attack, creatures in this terrain take 1d4 poison damage.
I used that one for the fungus forest in the second level of The Forge of Fury. I've done similar things for alchemist's labs, shops, taverns, and so on. Each natural 1 triggered a random, destructive effect.
Terrain and Stealth
I also use terrain to determine stealth. I shared this over on EN World, but after thinking about it I've adjusted it to make it easier for DMs who are not me to use.
Cluttered Terrain (X): While in this terrain, you can attempt to hide from creatures that are X or more feet away from you.
Cluttered can also have size or creature type requirement if we add an optional, second variable:
Cluttered Terrain (X, Y): While in this terrain, you can attempt to hide from creatures that are X or more feet away from you if you meet Y criteria.
Here's an example that's less programmer-ish:
Cluttered Terrain (5, size Small): While in this terrain, creatures size Small or smaller can attempt to hide from creatures that are 5 or more feet away from them.
In this case, an area might be filled with thick plants that are waist-high to a human. Small creatures can hide here, but larger ones blunder through it.
You can also treat light as an element of terrain:
Shadowed Terrain (X): While in this terrain, you can attempt to hide from creatures that are X or more feet away from you unless you are also in an area of bright light.
Dimly lit areas, even ones empty of blocking objects, default to shadowed terrain 15.
In running games, I've found this addresses the root question players have when it comes to stealth - can I hide from that creature or not? I can glance at a map, or estimate the distance, and provide an answer. It lets me avoid tracking where a creature is looking by abstracting the limit of vision based on terrain and light.
Tinkering with Darkvision
I also house rule that darkvision treats darkness as dim light. It does not treat dim light as bright light. Since creatures can hide in dim light in my games, darkvision is useful in dungeons but not an instant win button. A goblin can still sneak up on a dwarf, and there is a reason why torches and lanterns remain useful even for underground dwellers.
For me as a DM, this more abstract approach to terrain makes it much easier for me to create terrain that matters in an encounter. By starting with the effect I want, the encounter provides a better fit for the experience I'm aiming for while still giving players a clear view of how things work.
Messing with Stealth
I think stealth is in a weird place in 5e. The 2014 game didn't get it right, and both 3e and 4e ended up with grid-based stealth rules that worked OK until they didn't. Looking back, I'd use my rules above to create a simple check list for figuring out stealth.
You can try to hide from a creature if any of the following apply:
The creature has no line of sight to you
OR
You are in cluttered or shadowed terrain at their required distance
I'd then make the basic benefits of being hidden useful but somewhat lame. I'd let you move but not take actions. Taking an action - yes, any action - breaks stealth. You also break stealth if at any point you fail to meet either of the above criteria.
I'd then give monks, rangers, rogues, and certain subclasses the sneaky trait:
Sneaky: While hiding, you remain hidden when using sneaky actions.
I'd then add the sneaky tag to certain actions, like Sneak Attack or other custom design features, to make sneaky characters cool. Something like Sneak Attack might specify that you lose stealth on a hit but keep it on a miss.
In a class-based game, there is a lot of power in making something narrowly useful for most characters, and generally useful for specific characters who rely on that action. That's one design lesson I'd send back to 2012 to make 5e a better game.
Comments
Michael Sixel
I use it when my group is in a chaotic manifest zone, or in the abyss
Mark McDonald
This is great stuff. Running games you come up against things like this where you need a mechanic or ruling and doing it on the spot… forget it. This is a list I’d keep on hand. Also, the chaos themed stuff from the above poster would be great for my old Rod of Seven Parts game! Nicely done.
Ian Gray
The only drawback I can see with this is the extra workload this would place on the GM. They would have to rule each bit of terrain they place if not just for stealth.
