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Exotic Strongholds

Classic castles of stone with soaring parapets and open baileys where knights and soldiers tilt at the lists are iconic elements of medieval lore and literature, but in a fantasy campaign your castles can be so much more! The rules describe a wide variety of exotic materials that can be used for creating rooms, buildings, and fortifications, including cost, time, strength, and more. When you’re creating a stronghold as part of an adventure, however, you don’t necessarily need or want to go through the mathematical exercise of building a castle brick by brick.

What is more important is the challenge such strange strongholds present for your PCs and how to use them as an organic and exciting part of the campaign.

Table 4-1: Exotic Walls
Type Hardness1 Hp/Inch Climb DC Break DC
Bone 5 5 15 25
Cloud 0 0 102
Fire 0 (3)
Flesh 2 5 20 30
Ghostly 0 (3)
Glass 1 4 35 18
Ice 3 3 35 25
Insects 0 3 152
Magma 4 5 252
Ooze 0 3 0 202
Water 0 (4) 202
Web 0 2 20 202

1 Hit points per inch in parentheses indicate a wall that cannot be damaged by most forms of attack, but specific attacks listed in the wall’s description can damage it. The wall still can be dispelled even if it cannot be damaged.

2 This is the DC required to push through this semisolid wall, rather than to break it.

Elemental Strongholds

These strongholds form structures out of fundamental elements that are not usually solid and can be shaped and built only through magic or the intervention of powerful elemental beings. All elemental stronghold structures are held together by magic, and they can be unraveled with dispel magic that targets the elemental architecture spell that holds them together.

Cloud Castle

Skyfaring wizards and priests of the storm may craft castles from the congealed mists of the air, and cloud and storm giants are famous for their constructs among the clouds.

Walls: Cloud walls are formed of thick, semi-solid banks of cloud or mist bounded in by churning sheets of wind. Most cloud castle walls are opaque, blocking line of sight completely, but some might be semitransparent, only providing concealment to those behind the wall. A cloud wall affects creatures or objects entering it as a combined wind wall and solid fog.

Hazard: The semisolid vapors of a cloud castle wall are choking to air-breathing creatures trying to move through them. Creatures not holding their breath must succeed on a DC 15 Fortitude save or be nauseated with choking and coughing for 1d4 rounds after passing through the wall.

Sky Floor: The floors of a cloud castle are generally as strong as stone and cannot be pushed through like cloud walls can. However, the floor of a cloud castle can be made either opaque or transparent, showing the vast gulfs of sky below the floor.

Hazard: Creatures not native to clouds or lacking a natural fly speed become frightened (DC 15 Will negates) and overcome with vertigo when faced with a transparent sky floor, remaining frightened for 1d6 rounds plus a number of rounds equal to the amount by which they failed their save. After this time, they can attempt a new Will save to overcome their fright.


Red dragons, fire giants, mighty elementalists, priests of the burning gods, demons and devils who crave the ever-burning pyres love to surround themselves with living fire and may ply their mastery of magic to craft a home framed in flame.

Damaging Fire Structures: Fire structures are immaterial and cannot be damaged by most effects; however, they can be damaged by water or cold effects, using the hit points listed above. Fire structures take full damage from magical cold effects and take 1 point of damage per gallon from water.

Walls: Walls constructed of flame block line of sight but shed bright light within 20 feet and dim light within an additional 20 feet. Walls of flame have physical substance but are soft and permeable, equivalent to solid fog.

Hazard: A creature entering or beginning its turn within a wall of or other structure made of flame structure takes 4d6 points of fire damage. A creature moving adjacent to a flame structure or beginning its turn adjacent to a flame structure takes 1d6 points of fire damage. Fire walls typically give off smoke.

Floors: Magically solidified, fire floors cannot be passed through and are as hard as wood. However, they deal 1d6 points of fire damage per round to creatures entering or beginning their turn on an area of fire floor. A creature takes an additional 1d6 points of fire damage if it falls prone.


Molten rock can be shaped and formed into channels and sheets that flow in glowing sheets even as their surface cools into a smoldering crust only to crack and melt once again.

Damaging Magma Structures: Magma structures take half damage from most forms of attack, but they take full damage from cold effects. Water deals 1 point of damage per gallon to a magma structure.

Magma Walls: Walls constructed of magma are harder than fire walls, with chunks of solid stone floating and churning within them but are still only semisolid. Dealing 30 or more points of cold damage (or damage from water) to a magma wall in a single round causes it to solidify into a solid wall of unworked stone, with the hardness and hit points of typical stone. However, as long as any magma sections remain adjacent to sections of solidified stone, they re-melt 5 feet of stone back into magma every 2d6 minutes.

Hazard: Touching or beginning your turn touching a magma wall deals 2d6 points of fire damage. Strength check to push through. A creature passing through a magma wall takes 10d6 points of fire damage if they are able to pass through it on their turn with a single successful Strength check. Creatures remaining within a magma wall take 20d6 points of damage per round of exposure and must hold their breath or begin drowning.

Floors: Magma remains semiliquid when used as a floor, acting as difficult terrain and causing a -5 penalty on Acrobatics and Stealth checks for creatures moving through it. Water walk or similar magic allows a creature to step across the surface of a magma floor, taking only 2d6 points of fire damage each round they enter or begin their turn on an area of magma floor. A creature falling prone or beginning its turn prone on a magma floor takes 5d6 points of fire damage.

Water Walls

A wall of water may be a churning fluid mass held in place by elemental forces or a continuously renewing torrent cascading down in a perpetual waterfall.

Damaging Water Structures: Water structures take one-quarter damage from electricity, but creatures within the water wall take full damage from the electricity. Fire and force effects deal full damage to a water structure. A section of a water structure that takes 20 or more points of cold damage in a single round becomes an ice structure instead; however, if there is still a liquid water structure adjacent to an ice structure it begins melting the ice back into liquid water at a rate of 1d6 hours for each 5-foot section. A section of a water structure that takes 20 or more points of fire damage in a single round erupts in a cloud of steam that acts as obscuring mist within 10 feet of the water structure. This steam lasts for 1d4 rounds.

Water Walls: A water wall offers concealment to those behind it if it is less than 3 feet thick, or total concealment for thicker walls. Water walls cannot be climbed but can be ascended with a DC 30 Swim check. Moving through a water wall requires a successful DC 20 Swim check.

Hazard: The pounding torrent of a water wall deals 1d6 points of nonlethal bludgeoning damage per round (DC 15 Fort negates), and a creature failing its save is also knocked prone. Creatures with the fire subtype instead take 2d6 points of lethal damage per round, with no save allowed. A water wall poses a potential drowning risk for creatures unable to move through it or escape from it.

Floor: A floor of liquid water gains solidity through magic, treating it as a slippery surface (increasing the DC of Acrobatics checks by 5). Most water floors are relatively static, but some may support flowing water, which causes the floor to act as difficult terrain for creatures moving against the flow of water. Medium or smaller creatures running or charging in flowing water, whether moving with, against, or across the current, must succeed on a DC 11 Reflex save or fall prone and be pushed 1d4 x 5 feet downstream by the current. It is possible to create areas of open, non-solid water as part of a water floor. They are very difficult to distinguish from the surrounding water, requiring a successful DC 25 Perception check, with a +10 bonus if detect magic is being used. A rogue’s trap sense bonus also applies as a bonus on this check. A water walk spell allows a character to move easily across a water floor without impediment, whether the water is still or flowing.

Natural Strongholds

These strongholds are formed from naturally occurring materials and substance that can be shaped into strongholds with ordinary construction or through the application of nature magic.

Crystal Palace

The branching facets of crystal growths can be cultivated to massive size and forged into glittering palaces by the power of earthen magic and loving artistry.

Damaging Crystal Structures: Crystal walls take full damage from bludgeoning weapons but only half damage from piercing and slashing weapons. They take no damage from acid but take full damage from cold, electricity and fire, and damage from sonic effects is increased by 50% against crystal structures.

Crystal Walls: Walls of crystal or glass are not particularly strong, but some races favor them for their beauty. Crystal walls are generally translucent rather than perfectly transparent, blurring and distorting vision through walls and granting concealment to creatures on the other side of a crystal wall. Some crystal walls, however, may be as clear as glass and offer perfect visibility.

Hazard: Crystal walls typically are very slick and difficult to climb. While not difficult to break through, destroying a section of crystal wall causes it to shatter in a spray of shards. Any creature adjacent to a section of crystal wall when it is destroyed takes 2d6 points of slashing damage from razor-sharp fragments (DC 15 Reflex half), and all squares adjacent to the broken section are treated as if they were strewn with caltrops.

Floor: A crystal floor is generally very slick, treating them as slippery surfaces (increasing the DC of Acrobatics and Climb checks by 5), though they can be roughened to ease passage. A crystal floor is typically opaque or translucent, but a transparent crystal floor is clear as glass. If such a floor is used to bridge an abyss more than 100 feet deep, creatures traversing it that lack a natural climb or fly speed become shaken (DC 15 Will negates) until they can reach solid ground once again, at which point they can attempt a new saving throw each round at the beginning of their turn to recover their wits. Creatures that dwell on cliffs, high mountains, or other exposed heights may gain a circumstance bonus on this saving throw or may be immune, at the GM’s discretion.

Hedge Fort

Plants can be cultivated into powerful defensive structures comprised of tangled vines, living trees and shrubs, prickling brambles, and leathery greenery.

Damaging Plant Walls: Plant walls take only half damage from piercing attacks and acid and cold effects.

They take full damage from electricity and sonic effects, and fire effects deal full damage and overcome the wall’s hardness. As long ample sunlight and water are available, each section of plant wall regains 5 hit points per day, while a plant wall deprived on sunlight withers and dies over the course of several months. A plant growth spell can be used to repair all damage to one square of plant wall per caster level rather than having its normal effect. Tiny creatures can pass through a hedge wall with a DC 15 Escape Artist check, and Diminutive or Fine creatures can usually pass through plant walls without difficulty.

Floor: The floor of a hedge structure may be simple earth or wood, using the standard rules, but also may be cultivated vines and branches woven together. Hedge floors are unstable and full of potential gaps and trips. Creatures can move across a hedge floor at half speed without difficulty, but those moving at full speed must succeed on a DC 15 Reflex save or trip and fall prone at a random point during their movement. Creatures using feather step or similar effects that circumvent the effects of difficult terrain do not risk falling prone. In addition, hedge floors tend to be quite noisy, imposing a -2 penalty on Acrobatics checks and a -5 penalty on Stealth checks. These penalties do not apply to fey or creatures of the plant type, nor to Tiny or smaller creatures.

Hive Walls

In the sweltering jungle and the desert depths, endless swarms of insects and myriapods can be trained in their teeming masses to form living fortresses, with the carapaces of the dead merely adding to the bridges of the living as they continuously build and rebuild their mindless redoubts.

Damaging Crawling Walls: Crawling walls are made up of countless tiny insects and arthropods and can be damaged by effects similar to an enormous swarm. Crawling walls are immune to damage from weapons but they take 50% more damage than normal from area effects.

Crawling Wall: Walls formed of crawling bugs are not solid, requiring only a Strength check to force a way through. If a section of crawling wall is destroyed, the swarms that comprise it immediately begin to rebuild, extending the wall by 5 feet from any surviving sections each hour until it stretches back across the gap and reforms the wall.

Hazard: A creature climbing on a crawling wall or pushing through it is exposed to countless tiny bites, dealing 2d6 points of damage and becoming nauseated (DC 15 Fort negates) for as long as they remain in contact with the wall and for 1d4 rounds thereafter.

Floor: A floor carpeted in crawling insects, whether it is an ordinary floor covered in swarms or a magically suspended floor comprised of nothing but bugs, is unpleasant and unstable. The crunching of bugs underfoot causes a -5 penalty on Stealth checks, and an invisible creature’s location is easily marked by bugs crawling up and around their legs or any body part adjacent to the floor. These swarming insects deal no damage, but a creature beginning its turn prone on a crawling floor must succeed on a DC 11 Fortitude save or become nauseated for 1 round.

Special: A repel vermin spell causes a 10-foot-wide space to open in a crawling wall or floor.


In areas of perpetual cold, glacial ice can be harvested and formed into permanent structures, and even in subarctic climes ice can be shaped and formed into strongholds in the depths of winter or through the frigid enchantments of cryomantic sorcery.

Damaging an Ice Structure: Ice structures take full damage from bludgeoning weapons and half damage from piercing and slashing weapons. They are immune to cold and take only one-quarter damage from acid but electricity and sonic attacks deal full damage. Fire effects bypass an ice structure’s hardness and deal 50% greater damage than normal.

Walls: Ice walls can be translucent if carefully polished or only a few inches thick, but most ice structures are opaque.

Hazard: An ice wall does not deal immediate damage on contact, but creatures spending more than 1 minute in contact with an ice wall treat it as exposure to extreme cold. Walking on top of an ice wall is not as dangerous, treating it instead as a cold environment.

Floor: An ice floor is a slippery surface (increasing the DC of Acrobatics and Climb checks by 5), though permanent structures built atop ice floors may be strewn with gravel, sand, straw, or other material to provide better footing, making the surface only slightly slippery (increasing DCs by 2) or normal. Direct contact with an ice floor is not inherently dangerous unless there is prolonged contact. Treat a creature prone on an ice floor as being in an environment one step colder than the ambient air temperature.

Web Walls

In caves and forests, the same arthropod affinity that some use to force numberless insectoid hosts to form structures with their bodies can be applied to arachnids, silkworms, and similar spinners to weave massive structures of curtained webs. These web structures may be solidified with enzymes or interwoven with existing undergrowth to create sweeping bridges, chambers, and tangled corridors.

Damaging Web Walls: Web structures take half damage from bludgeoning and piercing weapons but take 50% more damage than normal from fire effects. A destroyed section of web wall can be repaired within 24 hours by the innumerable tiny spiders infesting the web wall and spinning new webs constantly.

Web Walls: Web barriers typically provide concealment and cover, but not total concealment or total cover, though some exceptionally thick web barriers may provide greater screening.

Hazard: A creature failing its Strength check by 5 or more when attempting to break through a web structure becomes stuck and entangled by the webs. Breaking free requires a successful DC 15 Strength check or Escape Artist check to escape back the way the creature came in, or a DC 20 check to break through to the opposite side. A trapped creature also can escape by dealing at least 15 points of slashing or fire damage to the webs.

Web Floor: A web floor may overlay an existing floor or may be a structure entirely made of webbing. In any case, its stickiness and unsteadiness makes a web floor difficult terrain, with a -5 penalty on Acrobatics checks but a +5 bonus on Climb checks to catch yourself when falling. Creatures with tremorsense have the range of that sense doubled when in contact with web floors, and spiders and similar web-dwelling creatures ignore the penalties other creatures suffer when traversing web floors.

Ooze Pile

Oozes can be congealed through magical and alchemical processes into gelid piles of semisolid colloid. Ooze walls are often constructed by alien entities or mad scientists. They may be created to stand on their own or as sickening sheaths clinging to stone walls underneath.

Structures made of deliquescent fungus are basically identical to those formed from ooze, though they also may hold poisonous or hallucinogenic spores.

Damaging Ooze Walls: Ooze walls take only half damage from bludgeoning and piercing attacks and are immune to acid. They take full damage from cold, electricity, fire, and sonic effects.

Ooze Wall: A wall of ooze is faintly transparent, revealing only vague shapes and shadows but providing total concealment. DC 20 Strength check to push through. A creature forcing a way through an ooze wall opens a hole that lasts only 1d4 rounds before closing again. A destroyed section of ooze wall repairs itself after 24 hours and returns to its former shape.

Hazard: Creatures touching an ooze wall take 2d6 points of acid damage, with no save allowed.

Floor: An ooze floor is a deliquescent rubbery mass, prone to squelch and suck at the feet of those treading upon it as their feet sink in up to the ankles. Ooze floors can be overlaid on an existing stone floor or can be magically crafted out of distilled ooze. Ooze floors are treated as difficult terrain unless creatures have freedom of movement or water walking and also impose a -2 penalty on Stealth checks. The location of invisible creatures walking on an ooze floor can be clearly marked by their sunken footprints in the ooze.

Hazard: Creatures entering or beginning their turn on an area of ooze floor take 2d6 points of acid damage per round. This damage does not increase if they enter multiple squares of ooze floor.

Necromantic Strongholds

Some structures can be formed only by tapping into the dark arts of necromancy, binding flesh, bone, blood, and spirit into a grotesque mockery of classical architecture.

Bone Keep

Simple bone structures are not uncommon among primitive societies, using collected bones for structure and for decoration, but the application of necromantic magic makes them far more dangerous.

Damaging Bone Structures: Bone structures take full damage from bludgeoning weapons and from positive energy. They take only half damage from piercing and slashing weapons.

Walls: Crafted from innumerable skeletal remains, bone walls are infused with necromantic power.

Hazard: The semi-animate bony climbs of a bone wall writhe and grasp at creatures climbing on them. A creature ending its turn climbing on a bone wall has a 50% chance to become entangled (DC 15 Reflex negates). An entangled creature can free itself with a DC 15 Strength check or Escape Artist check or can be freed by dealing 15 points of damage to the section of bone wall adjacent to the entangled creature. Dealing at least 15 points of positive energy damage to a semi-animate bone wall suppresses this entangling effect for 1 minute.

Floor: A bone keep’s floor is littered with skulls and bone fragments, typically a mix of light rubble and dense rubble, with many areas scattered with bony caltrops. Some areas may have grasping bones similar to those on bone walls.

Flesh Palace

Necromancers, demons, and other corrupt and cruel creatures may build fortifications from tormented flesh, melding the carcasses of the dead into a gruesome half-life of pulsating muscles and pumping blood.

Damaging Flesh Structures: Flesh structures take full damage from slashing weapons but only half damage from bludgeoning and piercing weapons. They take full damage from acid, cold, electricity, fire, and sonic attacks, as well as negative energy. Flesh structures have fast healing 5, and even if a section is completely destroyed any adjacent sections can regrow at a rate of 5 feet for every 24 hours, growing together towards the other side of the severed gap.

Walls: Walls of flesh may look almost vital, pulsing with vital fluids and prone to bleed if attacked, or they may be gray and putrefied, scabrous and rotting yet losing none of their revolting resilience.

Hazard: Flesh walls have embedded eyes and ears and can sense nearby creatures with a +10 bonus on Perception checks and 60-foot darkvision. In addition, a flesh wall has tremorsense with respect to any creature climbing on its surface, and any creature ending its turn on a flesh wall has a 50% chance to be attacked by gaping maw or tearing limb that reaches out from the wall (+10 attack bonus, dealing 1d12 points of bludgeoning, piercing, and slashing damage).

Floor: A flesh floor is often uneven and soft, with grotesque bulges in places and a quivering softness in others, along with lumps of tumors, bones, and sensory organs jut out. Flesh floors are equivalent to light rubble mixed with dense rubble, and they are reactive and prone to shift where the more difficult terrain appears. For true body horror, certain areas of a flesh floor might be so yielding and soft that they function like fleshy quicksand (see Environment), and flesh floors also might contain mouths or limbs that reach out to attack nearby creatures just as fleshy walls do.

Ghostly Redoubt

The most sinister fiends and necromancers extract the immortal essence of their victims and knit their soulstuff together into a tragic and terrifying tower of tattered ectoplasm.

Damaging Ghostly Structures: Ghostly structures are comprised of ectoplasmic spirit-stuff and can be damaged only by magical weapons and effects, taking half damage from all such effects other than force effects and positive energy (or attacks with ghost touch weapons).

Ghost Walls: Ghost walls have no physical substance and cannot be climbed. Their opaque gossamer shrouds offer total concealment but grant no cover against attacks through the wall. Dealing at least 30 points of positive energy damage to a ghost wall in a single round quells the spirits within the wall for 1 minute, making it save to transit that section of the ghost wall. A dispel magic spell (DC 20 caster level check) suppresses the binding magic holding the spirits within the ghost wall for 1d4 rounds, making the wall itself safe to traverse; however, this also temporarily looses the spirits within the dispelled section of wall to rampage and swarm over creatures nearby. Each round, the spirits flood out in a 30-foot cone aimed in a random direction from the dispelled section(s) of wall, affecting creatures in that area as if they had passed through the ghost wall, though the power of the scattered spirits is dissipated somewhat, reducing the save DC to 15.

Hazard: A creature passing through a ghost wall gains one negative level (DC 20 Fort negates) and takes 1d4 points of Wisdom damage (DC 20 Will negates) from the howling madness of the spirits.

Floor: A ghostly floor is typically made of ectoplasmic force, which is weaker than a true force construct with the hardness and hit points of solid wood. Incorporeal undead creatures can pass through a ghostly floor without difficulty, as if it were normal stone. A ghostly floor can be made either opaque or transparent. If a transparent ghost floor bridges an abyss more than 100 feet deep, creatures traversing it that lack a natural climb or fly speed become shaken (DC 15 Will negates) until they can reach solid ground once again, at which point they can attempt a new saving throw each round at the beginning of their turn to recover their wits. Creatures that dwell on cliffs, high mountains, or other exposed heights may gain a circumstance bonus on this saving throw or may be immune, at the GM’s discretion.

Hazard: Undead standing on a ghostly floor gain channel resistance +1 (+2 if they are incorporeal undead adjacent to the ghostly floor). This stacks with any other turn resistance they possess.

Section 15: Copyright Notice

Ultimate Strongholds © 2018, Legendary Games; Authors Ben Walklate and Jason Nelson.