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This is the DM’s map for running the Avernian hexcrawl. It’s designed for use with the Alexandrian Hexcrawl, as described in the 5E Hexcrawl series. We’ll be making some tweaks to this structure, however, to accommodate the unusual features of Avernus.
HEX SCALE
1 Hex = 40 miles (center to center / side to side) = 23 mile sides = 1385 square miles
The Avernian Hexcrawl uses 40 mile hexes. When tracking progress, this means it requires 20 miles of progress to exit a hex through one of the two nearest faces. (If they exit back through the face through which they entered the hex for a reason other than doubling back along their own trail, it requires 2d10 miles of progress to exit the hex, unless circumstances suggest some other figure.)
Design Note: The primary reason for choosing a 40 mile scale is because the PCs are likely to end up using infernal machines with much higher speeds of travel. The secondary reason is aesthetic: Avernus is supposed to be a wasteland. By increasing the scale of the hexes, we achieve that (increasing the average distance between points of interest).
OPPRESSIVE ENVIRONMENT
The conditions in Avernus are debilitating, alien, and severe, particularly for mortals. In addition to the normal encounter check, there is a 1 in 6 chance per watch that an oppressive condition will begin. Once begun, an oppressive condition continues until another 1 in 6 check per watch ends the effect.
d12 | Oppressive Condition |
1-3 | Extreme Heat |
4-6 | Choking Miasma |
7-9 | Psychic Evil |
10 | Acid Rain |
11 | Rain of Stones |
12 | Terrain Condition |
EXTREME HEAT: Temperatures reach extreme heat. A creature exposed to extreme heat must succeed on a Constitution saving throw at the end of each hour or gain one level of exhaustion. The DC is 5 for the first hour and increases by 1 for each additional hour. Creatures wearing medium or heavy armor, or clad in heavy clothing, have disadvantage on the saving throw. Creatures with resistance or immunity to fire damage automatically succeed on the saving throw, as do creatures native to Avernus. A successful saving throw while resting resets the DC to 5.
CHOKING MIASMA: Thick, noxious fumes fill the air. They may have a source (like volcanic clouds rolling off the mountains) or they may seem to rise from the ground or even just spontaneously emerge from the air itself. At the end of each watch, creatures must succeed on a DC 15 Constitution saving throw or suffer one level of exhaustion. Creatures who are resting gain advantage on the saving throw. Creatures with resistance or immunity to poison automatically succeed on the saving throw, as do creatures native to Avernus.
PSYCHIC EVIL: The supernatural evil of the Nine Hells weighs on the bodies and souls of those who are not evil. A non-evil creature must make a DC 15 Constitution saving throw at the end of each watch or suffer 1d3 points of psychic damage.
ACID RAIN: Thick purple clouds spatter the plains with burning acid. A creature without shelter suffers 1d6 acid damage per hour.
RAIN OF STONE: Small meteors pelt the plane. Creatures without shelter must succeed on a DC 12 Constitution saving throw each watch or suffer 1d6 bludgeoning damage per hour. There is a 1 in 10 chance per watch that the meteor storm intensifies, with blazing orbs of fire plummeting from the sky. Creatures without shelter must succeed on a DC 15 saving throw or suffer 5d6 fire damage and 5d6 bludgeoning damage.
TERRAIN CONDITION: Each type of Avernian terrain has an oppressive condition. This result on the table indicates that you should use the oppressive condition of the terrain in the expedition’s current hex.
As noted below, some terrain conditions do not persist. They occur once in the watch during which they are rolled, and then additional checks for oppressive conditions immediately resume in the next watch.
AVERNIAN TERRAIN
The wasteland of Avernus is scattered with rocks of obsidian and quartz. There’re mountains dotting the bloody-dusty plain, and foothills march across the land like the overturned tracks of some gargantuan, unknown beast. – Planes of Law (1995)
ASHLANDS: The ground here is covered in a thick layer of black ash, generally varying in depth form six to eighteen inches. The ash does not easily compress or support weight, so travelers will
often find themselves more or less wading through the ash.
Oppressive Condition – Ash Pit: In some areas the thin layer of ash is much deeper than it appears. Sentinels can attempt a DC 18 Wisdom (Perception) check to spot the ash pit as the expedition approaches. If no one spots the ash pit, 1d4 random characters in the expedition must make a DC 15 Dexterity saving throw or abruptly sink 2d4 feet deep in the ash.
At the start of each ash-bound creature’s turn, they sink another 1d4 feet into the ash. A character can attempt to escape by using their action to make a Strength check with a DC equal to 10 plus the number of feet they’ve sunk into the ash. If they have become completely submerged, they suffer disadvantage on this check and also begin suffocating.
Ash pits do not persist as an oppressive condition.
BONE BRAMBLES: A maze of warped trees and bonelike vines. Calcified corpses merge with the trees, covered in fungal pods that feed on the blood oozing through the undergrowth.
Experienced Avernian explorers know that bone brambles often grow up around sources of fresh water.
Oppressive Condition – White Mists: The brambles exude a thick, cloying, almost oily white mist. This creates a condition of poor visibility (halving moving speeds and giving disadvantage on navigation and forage checks). The mist is almost refreshingly cool by Avernian standards, but there are strange whispers and disturbing groans that come and go among the mists.
CAUSTIC BOGS: On the current map, the caustic bogs are formed from the polluted run-off from Bel’s Forge (Hex H2), but similar areas can be found across Avernus,
horrific remnants of the Blood War.
While travelling through the caustic bogs, characters must succeed on a DC 12 Constitution saving throw each watch or gain the Poisoned condition. The character can repeat the saving throw every 24 hours, ending the effect on itself on a success.
Oppressive Condition – Caustic Pollution: Characters must succeed on a DC 15 Constitution saving throw or suffer 1d3 acid damage.
HILLS, AVERNIAN: Either low mounds that undulate out of the wastelands or jagged
promontories of razor-like rock that jut toward the blood red sky. The native life of Avernus, such as it is, often clings and clusters in the hills.
Oppressive Condition – Scree: See the Wastelands terrain below.
MOUNTAINS, AVERNIAN: There are generally two types of mountains in Avernus. Newer mountains that thrust up like broken blades of obsidian; raw and dangerous. And the older mountains that have been worn down by countless aeons, their gray immensity aching with an age incalculable to the mortal soul.
Oppressive Condition – Tremor: Avernus in general is tectonically unstable and this effect is magnified along the mountain crests. This condition indicates a tremor significant enough to disrupt travel, imposing a x ¾ speed modifier for the current watch. 1 in 10 such tremors are more serious, triggering significant hazards like an avalanche, rockslide, cave collapse, or the like.
This does not persist as an oppressive condition.
PLAINS OF FIRE: An iridescent, tarry putrescence seeps up through the soil here. These alchemical slicks catch on fire, a combination of small ever-burning wells and
huge infernos miles long and high.
Failing a navigation check in the plains of fire, at the DM’s discretion, may indicate that the group has gotten cut off by a rapidly spreading fire, trapping the PCs in the eye of a firestorm.
It is never considered a clear day in the Plains of Fire.
Oppressive Condition – Extreme Heat: As described above.
PIT OF SHUMMRATH: A grand canyon more than a mile deep and filled with a lake of green slime that undulates as though breathing. The slime is actually the protoplasmic residue of an ancient devil imprisoned here by Archduke Bel many centuries ago, still possessed of some residual sentience and a telepathic ability to communicate (see p. 100 of Descent Into Avernus).
Large sections of the Shummrathian slime actually have a very thick skin, allowing the brave and foolhardy to walk across its slightly undulating surface. In slightly less gelatinous sections of the Pit, barges can dredge their way across.
Oppressive Condition – Telepathic Agony: An overwhelming telepathic burst emanates from the canyon, communicating in a single searing thought the eternal agony of Shummrath’s shattered consciousness. Characters must succeed on a DC 15 Wisdom saving throw or suffer 2d6 psychic damage.

WASTELANDS: The wastelands of Avernus look like sand, but are mostly made up of
hard, sharp rocks akin to the quartzes and obsidian of the Material Plane. Footing can be treacherous.
Oppressive Condition – Scree: Traveling characters must make a DC 12 Dexterity saving throw each watch or suffer 1d3 damage. A character failing the saving throw must immediately attempt another, repeating until they succeed on a check or choose to stop traveling (in which case their distance traveled for the watch is halved).
WASTELANDS, CRACKED: The surface of Avernus is a rotten rind stretched across a
festering fruit. In places, the ground has split apart. In cracked regions of the wastelands, the land is riven with fissures and ravines. Navigating these regions is difficult, either requiring great effort to circle around impassable chasms, or maze-like passages through the fissures themselves.
Oppressive Condition – Scree: See the Wastelands terrain above.
VOLCANIC PLAINS: Vast, smooth plains of black, basaltic rock. Sometimes shattered by tectonic upheavals. Often studded with fissure vents and bubbling pools of fresh lava.
An unusual feature of Avernian volcanic plains are the kipukas: Isolated areas of older lava flows surrounded by newer flows. On Avernus, these kipukas are often etched with the
characters of some ancient and utterly forgotten tongue.
Oppressive Condition – Volcanic Event: Journeying near an active volcano is, of course, not safe in any circumstances, and even less so given the churning activity of a typical Avernian caldera. There are several volcanic events that could arise as an oppressive condition.
- A choking miasma of volcanic gas (see Oppressive Environment, above). More serious outbreaks of volcanic gas are also possible; resolve as a cloudkill
- An active lava flow, blocking the desired path of travel.
- A tephra fall, in which multiple inches and even several feet of ash can fall as precipitation. Add +2 to the DC of navigation checks and +4 to the DC of forage checks.
- A lahar, a violent mudflow formed from a slurry of pyroclastic material. (Resolve like an avalanche.)
- An eruption. This might be modeled by requiring the PCs to flee the hex within a certain timeframe.
Terrain | Highway | Road/Trail | Trackless | Navigation DC | Forage DC |
Ashlands | x1 | x1 | x ½ | 12 | 24 |
Bone Brambles | x1 | x1 | x ½ | 18 | 16 |
Caustic Bogs | x1 | x ¾ | x ½ | 15 | 20 |
Hills, Avernian | x1 | x ¾ | x ½ | 14 | 18 |
Mountains, Avernian | x ¾ | x ¾ | x ½ | 16 | 22 |
Plains of Fire | x1 | x ¾ | x ½ | 14 | 24 |
Pit of Shummrath | x1 | x ¾ | x ¼ | 15 | 22 |
Wastelands | x1 | x1 | x ¾ | 12 | 20 |
Wastelands, Cracked | x1 | x ¾ | x ½ | 16 | 20 |
Volcanic Plains | x1 | x ¾ | x ¾ | 12 | 24 |
Note: Although values are given for Highway speed, there are no such causeways in this section of Avernus. (They’re quite rare in Avernus in general.)
THE STYX
The effects of the River Styx are described on p. 76 of Descent Into Avernus.
It should be noted that these effects apply only to the waters of the river itself. The Styx is fed by a number of tributaries which do not share these effects until they join the main channel of the Styx. In Avernus, these tributaries may be water, but are more likely to be fouler effluvia. (In places within Avernus there are whole systems of rivers and lakes filled with nothing but the blood and bile and other fluids of mortal creatures spilling down into the Styx.)
NAVIGATING AVERNUS
Avernus… Its blasted, rock-strewn fields gape like festering wounds under a crimson sky. Neither stars nor sun brighten the infinite reach of this layer’s sky, for the blood-red light emanates from the air itself. There’s no way to keep time in Avernus, save by the screaming of the [suffering]. – Planes of Law (1995)
COMPASS DIRECTIONS: Cardinal and ordinal directions don’t exist in Avernus. (There is no rising sun, no stars in a night sky, and no magnetic field for aligning compasses.) This imposes disadvantage to navigation checks until a navigator has adapted to the oddities of Avernian geography (by successfully reaching an intended destination for the first time).
PLANAR COMPASS: A planar compass is a technomantic device which allows for navigation in the Outer Planes. A planar compass aligns to the nearest planar borders. In this particular region of Avernus that corresponds to the planar borders with Dis (to the “north” side of our map) and the Abyss (to the “east”). Thus Dis-ward, Abyss-ward, contra-Dis, and contra-Abyss.
Design Note: For simplicity, you might still want to use the familiar cardinal directions at the table. Here’s one way you could justify that: The word “north” actually derives from a word meaning “left” because it was the direction to the left of the rising sun. You could hypothesize an Avernian dialect in which the direction towards the Abyss (and the front lines of the Blood War) is adversa, and “Avernian north” is the direction to the left of that. In translation to the Common tongue, the common names – north, east, south, west – are extrapolated accordingly.
SIGHTING MOUNTAINS: In the absence of stars, sun, or magnetic fields, navigation in Avernus relies heavily on landmarks. In this particular region of Avernus, this is greatly aided by the Dispatrian Mountains that lie Dis-ward and the Praefervian Mountains to the contra-Dis.
On a clear day, both mountain ranges can be seen at a distance of two hexes (80 miles), but will frequently only be visible from 1 hex away. The thick haze of the Avernian atmosphere, however, usually reduces this to a single hex. Volcanic peaks indicated on the map (like Bel’s Forge in Hex H2) can similarly be seen at a distance of 1-2 hexes.
IDENTIFYING MAP LOCATIONS: If the PCs make inquiries, assume that Avernian natives can identify 1d6-1 locations on the player’s map.
OTHER AVERNIAN GUIDELINES
FORAGING: Food and water – particularly that suitable for mortal consumption – is hard to come by in Avernus. The native flora and fauna have a bitter or ashen flavor, and even drinkable water usually tastes foul.
Mortals make forage checks in Avernus at disadvantage. (Hell is not a place for mortals.) This does not apply to characters with demonic or devilish heritage (such as tieflings), who will find a broader range of Avernian wildlife suitable for their palates.
SPOTTING DISTANCE: Avernus is flat, which means there’s no horizon to block vision. With a clear line of sight you could hypothetically see an infinite distance… if it wasn’t for the atmosphere. On a perfectly clear day on Earth you can see about 150 miles through the atmosphere, but such conditions are rare on Earth and virtually impossible in Avernus.
Assume a 1 in 6 chance of a clear day.
On a typical day:
- A character taking the Sighting watch action can see their current hex.
- Mountains can be seen 1 hex away.
On a clear day (by Avernian standards):
- A character taking the Sighting watch action can see 1 hex (40 miles) away.
- Mountains can be seen 2 hexes away.
- Encounter spot distances in plains- or desert-type terrain (ashlands, wastelands, volcanic plains) are doubled. (Emphasize the disorienting nature of seeing creatures at such great distances to those unaccustomed to planar travel.)
UNSUITABLE TERRAIN: Land vehicles perform poorly in unsuitable terrain. Infernal war machines are well-suited to the Avernian wastelands, however, and are likely to only find mountainous terrain unsuitable. At the DM’s discretion they might also find unusual terrain like the Pit of Shummrath or the caustic bogs similarly problematic.
Some map icons from Hells Upper Levels by Keith Curtis via Inkwell Ideas.
Additional icons by Kevin Chenevert of RedKobold.com.
Go to Part 7C: Avernian Hex Key