Dragon Encounters

Making dnd combat fun, finding monsters that fit together, monster tactics and strategies, and other ways of using the monsters of dungeons and dragons

DARKMANTLE: Traps and Obstacles in the Dark


Combat rating 1


1 Darkmantle (CR 1/2)

3-4 Giant bats (CR 1/4)


Combat rating 1


1 Darkmantle (CR 1/2)

3-4 Grimlocks (CR 1/4)


Combat rating 2


2-3 Darkmantles (CR 1/2)

2 Grey oozes (CR 1/2)


Combat rating 3

1-2 Darkmantles (CR 1/2)

5 Rust monsters (CR 1/2)

How to Use

The darkmantle’s basic tactics are to use its false appearance until prey gets within reach, then use a turn to activate its darkness, and only then to latch onto the target. It can’t latch onto the target first, or there is a good chance that it will be killed before it has a chance to activate its darkness.

Uses With Other Creatures

Let’s start with the most basic ways you can use the darkmantle. In addition to the basic attack, there is:

  • Have the players arrive when the darkness has already been activated by some other creature. If the players enter, they might end up surrounded by a bunch of foes when the darkness lifts. Or with only one or two powerful foes, but they are spread out, with one of the mages uncomfortably close to the enemy.
  • Before the darkness is lifted, their situation will be even worse. After all, there are other beings in the cave, but who can tell whether they are friend or foe. While there isn’t any silence spell in effect, that doesn’t mean that they speak the same language as the others. In addition, people rarely have the calm of mind to talk rationally while under active attack. [This last one applies to both the players and the NPCs.]
  • If they have reason to believe that there are allies/friends in the area, or just good-aligned NPCs, the situation becomes even more complicated for them. Should they strike back? What if they end up alienating or killing their allies? But if they don’t fight back, they might be in trouble if the others are monsters/enemies.
  • It’s also worth noting that inadvertent blows during the darkness can easily lead to further fighting after the darkness is lifted. Even if the players restrain themselves, that doesn’t mean the NPCs will. Let’s see how the players deal with it when a hotheaded member of the NPCs attacks them. Also, many non-damage spells [Hold Person, Slow, Tasha’s Hideous Laughter, and many more,] can be used to restrain the players in the hope of calming down the situation, but can also be mistaken by the players for an attack. See what happens.

Combat Scenario 1: Pits in the Dark [Battlemap variant] (Difficulty 3)

This one is simple. Make a battlemap which contains numerous pits. They can be either traps set against them or natural chasms. (If they were dug as pits, I would expect numerous small [one or two squares or hexes] holes scattered around the map. If they’re natural chasms, I would expect a few wide lines that cross a good portion of the battlefield [although it might move in and out.])

You’ll need two copies of the battlemap. One of which will be hidden behind your DM screen, the other available to the players. You’ll need a paper, preferably black, to put down upon the general battlemap when the entire party is affected, and a circle the size of the darkmantle’s darkness [I.E., with a six-square circumference] for when only one or two PCs are affected. Ignore the fact that the player surrounded by darkness will also see ahead, as well as the fact that all the players will see the other side of the darkness, which they shouldn’t be able to see. You can only do so much.

This can be used as an obstacle course, like the other scenarios down below, but it will work much better as a fight, used together with several other enemies. I would suggest also having more than one darkmantle, although you might not have more than one at a time. They wait for someone to get close before striking.

Combat Encounter 2: Obstacles/Traps in the Darkness (Difficulty 3)

Another, significant use of darkness is when the players are forced to navigate an area studded with minor obstacles, and/or traps. I am going to give a number of different types of obstacles and traps, and notes as to how darkness will affect them, but before I can do that, I need to handle another matter.

The most logical thing for the players to do when they encounter a darkmantle is to first fight it off, and only then to resume moving forward. If you want to use the darkmantle as an excuse for forcing them to navigate these obstacles and/or traps in the dark, you need to find a reason for them not to do so. The most obvious is some kind of time limit. Below are three different types:

Type 1: The simplest is just to set up a time limit that they know of beforehand. Perhaps a certain door through which they wish/need to enter is only open for a specific minute each day. Perhaps they’ve been told of a 1-minute time when the guards change and there is no one there. Or perhaps there is a powerful guardian golem, one too powerful for them to fight at their level, but due to a mistake in its construction it isn’t operational for a specific minute each day.

You’ll also need a reason why they didn’t enter earlier, that way they could have passed through the area and then waited around for that minute to arrive, but that part is easy. Just put a second door, guard, guardian golem or whatever at the beginning of the path that also has to be passed through that minute. Then they only have a minute to get through the whole course. (I would, once again, caution you to have a plan for if they fail. If you simply rebalance it and announce that they got lucky and had extra time, you ensure that they won’t take future time limits very seriously.)

Type 2: Another option is the advancing screen made popular by Mario and similar video games. As the players enter the area, have them trigger an unavoidable trap. The area behind them starts to fill with poisonous smoke, which will continue to advance every single round until it covers the area.

Unlike in Mario, where getting caught in it [between it and a wall, technically] means instant death, here I would just have it do a small amount of damage. I would suggest 1 HP per every two players levels [use average party level. Don’t penalize different players differently.] While this is negligible, it’s affecting every player, every round. And don’t forget that they will also be taking damage from other sources.

You might want to raise the damage slightly if they get too far back in the smoke, as in raising the damage for an area the longer it’s been affected by smoke. This way they can’t decide to take the damage in exchange for having time to fight off the darkmantles.

I would suggest using a dice to see how fast the smoke advances [probably between 10-20 feet a round.] If you decide each round the players won’t feel pressured, and if you use a set amount it will be hard to adjust it if the players are doing too well or too poorly. This way you can just fake a dice roll, or change the rules of the dice roll.

Type 3: The third way is to use enemies. If there are enemies in the area then they are going to want to move around, simply to fight them efficiently. Alternatively, there might be enemies behind them, and they need to keep moving before these enemies catch up. This way is tricky, because you need to have a plan in case the enemies catch up. (Some form of taking the PCs prisoner is the most obvious solution.)

A third variant is to have the enemies remain outside the darkness and be making ranged attacks at them (drow with arrows would seem the most likely.) This variant even gives them a reason to think twice about killing the darkmantle, as its darkness is helping them escape the arrows. (In addition to the disadvantage, I might make no more than one in two or three even need to be rolled for.) Just remember to put the enemies in front of them rather than behind, if you don’t want them going to wrong way.

Even with these methods, it seems logical that they will kill the darkmantle. Therefore, you will want to use more than one darkmantle in your obstacle course. It is normal for several of a low CR enemy to be found in the same area, and the periods of sight in between dealing with different darkmantels can be folded into challenge. Use a bunch of twists and turns as the path goes around corners to stop them from seeing too far ahead.

I am going to present a list of obstacles and another list of traps. That does not mean that you should use all of them. One of them, together with a single darkmantle, also makes a nice obstacle, and doing so means you can be more relaxed with the time limit I suggested earlier. (Since the difficulty isn’t so great, the failure of managing on time can be similarly less. Perhaps just a few enemies in the region, who will catch up to them or detect them if they don’t go fast, and the penalty of failure can be having to fight an extra fight.) The natural obstacles and the traps can be combined, or used separately. (My recommendation, for a difficult area guarded by enemies, would be two obstacles and one trap.)


  • A River Lies Ahead: The party will hear the rush of water, but they won’t know that the path turns ahead next to the water. If they keep going, they’ll fall in, and the water’s current will pull them along and smash them into rocks. Even once they pull themselves ashore, they might have trouble reversing their footsteps. There isn’t necessarily a bank at the side of every part of the river, and the river is going a bit fast to follow along inside the river. If you want to make matters worse, put a waterfall downstream. (Pits can also be used, but their effects tend to be either minor or instant death. Also, rivers give an audible warning.)
  • Loose rubble: Put the rubble at the top of a slope that they are going to be descending. When descending, this gives a large chance that they will slip and start to fall, taking falling damage and landing prone. The real danger will come when the other players start to descend, however. If they knock a boulder down, they’ve basically activated a boulder trap and sent it toward their fellow player. And the rubble that they knocked loose might bury him, especially if he’s prone.
  • A Wall Lies Ahead: The front PC smacks his face into a wall. After feeling around, they realize they have to climb it. (You probably should make the tunnel narrow, and add a draft or a sound coming in from above. If not, they may feel around until they get frustrated, and then kill the darkmantle.) If it’s tall, they’ll have to worry about finding handholds without being able to see, and perhaps climbing partway and then realizing there’s nowhere left to reach. Also, rocks coming free under their hands/feet. If it’s not tall, they can boost each other, and have to worry about slipping. Add in a series of small cliffs going up, or some going up and some down, for more variety.
  • A Split in the Path: The path splits up ahead. Unfortunately, the party doesn’t notice, and some go left, some go right. You’ll want to let them know before too long, but there’s still time for a single encounter that the two groups will fight separately, or for them to come out in the same place on different sides of a river or on different elevations. (You could also go for a maze, but keep in mind that 3-D mazes need to be kept simple, and even more so when they are shrouded in darkness. 3-4 dead ends, or 2-3 places where the path loops around and deposits them back where they started from are plenty.)

There are also a number of obstacles that aren’t much by themselves, but are nasty when combined with another monster or two. (Choose 1-2 low-level monsters. [I favor grimlocks as they are blind and can ignore darkness.] Remember that they have the obstacles and the darkness to deal with as well.)

  • Slippery Floors: Perhaps because of water dripping from above, perhaps spots of slime or fungi, the floor has been left with slippery spots. Make a note of a handful of areas that will contain slippery spots on your personal battlemap (the one you’ll keep behind the DM screen). If the step on one of those spots, roll a dice. Depending on what you rolled, you’ll decide whether they stepped on a slippery spot. If they did, they fall prone.
  • Collapsible Cave: The roof of this area is delicate. If they use area-of-effect spells carelessly, or perhaps if they are careless with traditional weapons, they’ll bring the roof down upon themselves. This can be a rockfall, where they take damage from falling rocks, or this can be a collapse, where a section of area becomes impassible and some of them might end up pinned to the floor.
  • Stuck in a Crack: For a harder approach than the last two, have a crack in the floor with loose stones in it. When the PC accidently steps in it, the rocks settle around his foot, and he’ll need considerable help [and a pickaxe] to widen the crack and let his foot free. You can also use a boulder that rolls over and pins the PC underneath it, or combine it with one of the last two ideas to have the PC trapped by a falling stalactite or slide into a crack. And for the worst-case scenario, the PCs entire body gets stuck in said crack.

Traps: (Note: if you’re going to use the same trap multiple times, place it in just a single stretch of area. To do otherwise while using darkmantles is unfair to your players.)

  • Crossbow Traps: You know the type, a tripwire laid across the ground that’s connected to a crossbow that’s primed to fire. With vision, this is where we have the boring “Roll to detect trap, roll to disarm trap” without vision, they’ll have to be pretty inventive to figure out that a way to detect the trap. (Note: Crossbows fire at an area right before the tripwire.) If you want to play fair, have them hear their enemies sniggering about “Something: right before the first trap, to give them a clue.
  • Tripwires: In addition to the above, they can be used to make them fall, with spikes and/or a pit on the other side of the tripwire. If they want to go slow in order to detect such tripwires, they can. That’s why we added a time limit. (Make the first one minor, as it’s a sucker punch. The challenge is how to they avoid future tripwires.)
  • Boulder Trap: They’re ascending up a slope when they hear a rumbling sound ahead of them. If they ask, tell them it sounds like something heavy moving. Shortly before this trap is triggered, you should put a platform at the side (this itself might confuse them and make them think dead end, given that they’re blinded,) and if they don’t move onto it fast enough [in game time or in real time] they’ll get flattened by the boulder.
  • Collapsing Bridge: They’re crossing a narrow bridge, probably over a river, and as the front player reaches the 2/3 mark, he feels the bridge starting to come apart under him. If he jumps backwards, he probably won’t make it [I’d go as high as DC 18 [athletics]. Remember, he’s facing the wrong way, he was taken by surprise, and he has only moments.] If he jumps forward, he’ll probably make it, [I’d give him an automatic success, actually] but the party will be on two different sides of a river. (If some or all of the PCs were crossing the bridge at the same time, you’ll have to decide where the others were standing, and judge their actions accordingly.]

Combat Encounter 3: Darkmantle Swarm (difficulty 5)

Like with other creatures of low CR, there’s no reason why multiple darkmantles shouldn’t live together. Select a number, probably 2-3 per player, and have them all attack the PCs in one big mob. Invariably, one player will pull free before the others, and he will have to decide who to help. (While the darkmantles do small amounts of damage, it will quickly accumulate. And that’s without the suffocation.)

When doing this, you’ll want to decide on the area. A small area has the advantage that they won’t wander away from each other (their best strategy would be to work together to free one player), while a large area has the advantage that once one player breaks free of the darkmantels attacking him, he’s no longer in darkness and can form a better plan of attack. If you choose a large area, you can decide whether the floor is the same all other, or otherwise. If the floor varies it will help the players find each other. (Though if you make two identical areas it will create a lot of confusion.)

I should also note that if your players are level five or higher, you’ll need to protect the darkmantles from being wiped out by one Fireball (or similar spell). One solution would be to make the area wide enough that one fireball won’t hit everywhere, and have the darkmantles arrive in two waves (in which case you might want to make the total number 3-4 per player.) Another solution would be to make the area prone to collapse, perhaps verifying this fact in a previous encounter.

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About Me

I have been a DM for several years, and I was designing home RPG games since my young childhood. I have been a fan of many different types of games (computer, board, RPG, and more) and have designed several for my own entertainment. This is my first attempt to produce game content for a wider audience.