Skip to content
CharGen Icon
CreatePricing
Brineweight - AI-generated fantasy Monster

Brineweight

Trench crews speak of the Brineweight as a moving hazard that can flatten a salvage rig or turn a safe passage into a boiling choke point. Its intact plates are said to outweigh an entire crew's haul. Those who have watched it feed claim it is drawn to something beneath the vent fields, though no one agrees what that means.

Monsters
Gargantuan elemental · CR 16 , deadly solo threat for many parties, especially in confined or submerged terrain. · Unique

Brineweight

A gargantuan geothermal elemental whose basalt shell channels crushing pressure, boiling brine, and ley energy through the Abyssal Trench.
AC18
HP297/297
CR16 , deadly solo threat for many parties, especially in confined or submerged terrain.
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 18 · HP 297 · CR 16 , deadly solo threat for many parties, especially in confined or submerged terrain.

Brineweight

Gargantuan elemental (elemental), unaligned
Armor Class18
Hit Points297 (17d20 + 119)
Speed
Speed 20 ft.,
Swim 40 ft.
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsConstitutionWisdom
Damage Resistances
Cold,
Force
Immunities
Fire,
Poison,
Exhaustion,
Paralyzed,
Petrified,
Poisoned
Weaknesses
Slow movement on land makes it vulnerable to characters who retreat and maintain distance.
It can be calmed by a steady rhythm when no one attacks, allowing a noncombat resolution.
Senses
Blindsight 120 ft.,
Passive Perception 12
Languages
None
Challenge16 , deadly solo threat for many parties, especially in confined or submerged terrain.
Initiative+0 (10)
Proficiency Bonus+5
Legendary Resistance3/Day
Spell Save DC20
Melee Attack Bonus+11
Legendary Resistance. If the Brineweight fails a saving throw, it can choose to succeed instead. It can use this trait three times per day.
Arcane Feedback Shell. When the Brineweight takes damage from a spell of 5th level or higher, it regains 16 () Hit Points and releases a shockwave. Each creature within 10 feet makes a Dexterity saving throw or takes 10 () Force damage.

Actions

Multiattack. The Brineweight makes two Crushing Claw attacks and one Basalt Limb attack.
Crushing Claw. Melee Attack Roll: +11, reach 15 ft. Hit: 28 () Bludgeoning damage plus 9 () Fire damage.
Basalt Limb. Melee Attack Roll: +11, reach 20 ft. Hit: 22 () Bludgeoning damage plus 7 () Force damage.
Boiling Geyser Blast. Recharge 5–6. Constitution Saving Throw: , each creature in a 60-foot Line that is 10 feet wide. Failure: 44 () Fire damage plus 22 () Force damage, and any metal armor the target wears becomes superheated. The target takes 10 () Fire damage at the start of its next turn. Success: Half damage only, and no superheating.
Ley-Surge. Recharge 6. Dexterity Saving Throw: , each creature in a 20-foot Emanation. Failure: 31 () Force damage. Success: Half damage only.

Reactions

Superheated Pressure Hull. When a creature hits the Brineweight with a melee attack, the attacker takes 10 () Fire damage.

Legendary Actions

Trench Crawl. The Brineweight moves up to half its Speed without provoking Opportunity Attacks.
Crushing Sweep. The Brineweight makes one Crushing Claw attack.
Pressure Pulse (costs 2 actions). Each creature within 20 feet makes a Constitution saving throw. Failure: 22 () Force damage and the Prone condition.
Role
Legendary brute and environmental hazard
Built for
Designed for a level 16 party; CR 16.

Notes for the game master

Custom monster, not an official 5e creature.
Legendary Actions: 3 per round, one at a time at the end of another creature's turn. The Brineweight regains all spent Legendary Actions at the start of its turn.
Arcane Feedback Shell triggers when the Brineweight takes damage from a spell of 5th level or higher. It regains 16 (3d10) Hit Points and each creature within 10 feet makes a DC 20 Dexterity saving throw, taking 10 (3d6) Force damage on a failure.
The Brineweight's attacks and area effects use the supplied damage and save values.

Tactics

  1. Opening

    If surprised or approached aggressively, open with Boiling Geyser Blast along the densest approach. If opponents are spread out, use Ley-Surge to disrupt their formation before closing.

  2. Mid-fight

    Use Crushing Claw against adjacent threats and Basalt Limb against targets trying to stay beyond claw reach. Line up Boiling Geyser Blast through clustered enemies, especially those wearing metal armor.

  3. End of the fight

    When badly injured, use Ley-Surge to scatter nearby enemies, then crawl toward deeper water or a vent channel. It fights to protect its feeding ground, not to pursue prey across open land.

  4. Retreat

    The Brineweight does not flee from pain in a human way, but it withdraws when its shell is cracked and attackers stop pressing. A steady pressure-plate rhythm or diverted magical energy may calm and redirect it.

How it fights

Use its long reach to threaten characters who assume that staying outside claw range is safe.
Position it so Boiling Geyser Blast threatens a line of characters while leaving a visible escape route.
Use Pressure Pulse after enemies close in, then crawl toward isolated targets.
Do not have it chase far onto land; its slow movement is an intentional counterplay opportunity.

Who it attacks first

Creatures attacking its shell or disturbing its vent basin.
Targets clustered in a geyser line or within the pressure-pulse radius.
Metal-armored creatures positioned in the path of Boiling Geyser Blast.

Works well with

Works especially well in a geothermal trench with hazardous vents and limited escape routes.
Siphon machinery or unstable ley conduits can give the party a reason to redirect rather than kill it.
Serves as a formidable guardian near extraction crews, pressure stations, or a passage sustained by geothermal heat.

How to beat it

Its land Speed is only 20 feet, so mobile characters can retreat beyond its reach on open ground.
Keep the party out of the 60-foot line of Boiling Geyser Blast and avoid clustering within its 20-foot Ley-Surge area.
A DC 20 Wisdom (Animal Handling) check can soothe it by matching the steady click of its pressure plates, provided no one attacks.
A controlled release of magical energy can divert it from a threatened passage or settlement.
Its Arcane Feedback Shell rewards care with high-level spells; use other tactics or accept the risk of its healing and shockwave.

Ways to avoid a fight

A character can attempt to soothe it with a DC 20 Wisdom (Animal Handling) check, matching the regular clicks of its pressure plates. No creature can be attacking it during the attempt.
A controlled release of magical energy can draw it toward a safer channel or away from a settlement.
The party can investigate what the Brineweight is feeding on by tracking its movements and examining the vent basin, without harvesting its plates.

Ecology

A moving cliff of black basalt and pale salt-crust, the Brineweight bears immense overlapping pressure plates, each slick with brine and rimmed in orange geothermal glow. Its claws grind against stone with a sound like a ship dragged over gravel. Green-blue light flickers through seams in its shell, and the water around it shimmers with heat.

Behavior

It advances with slow, crushing steps, reading movement through pressure changes in water and stone. It reacts violently to abrupt magical surges and close attacks, but can be soothed by a patient, rhythmic signal when no one threatens it.

How it lives

The Brineweight inhabits deep geothermal channels and ley-fed vents, where it appears to draw sustenance from heat and magical pressure. It is not known to hunt for food in the ordinary sense. Trappers prize an intact pressure plate, though removing one may disrupt the vent system the creature has been feeding on.

Lair

It settles in a deep vent basin where geothermal jets escape through cracked basalt. The floor is littered with shattered stone and discarded salvage, while unstable pressure pockets make careless movement perilous.

Habitat
Abyssal Trench geothermal vents, submerged basalt shelves, pressure-sealed extraction sites, and ley-active channels in the Frostmelt Archipelago.

Signs that it is near

Freshly fractured basalt with broad, deep gouges.
Brine bubbling through cracks in the seabed despite the surrounding cold.
A repeated clicking sound that can be felt through hulls and stone.
Salvage equipment crushed flat and warmed through with no obvious fire.

Tags

elemental,
gargantuan,
legendary,
geothermal,
trench,
custom

Lore

Trench crews speak of the Brineweight as a moving hazard that can flatten a salvage rig or turn a safe passage into a boiling choke point. Its intact plates are said to outweigh an entire crew's haul. Those who have watched it feed claim it is drawn to something beneath the vent fields, though no one agrees what that means.

What drives it

It is driven to remain near its geothermal feeding ground and to repel threats that disturb its shell, pressure channels, or vent basin.

After the fight

When the Brineweight falls, its pressurized shell vents in a long, rattling sigh. The water around it warms, then goes strangely still. Salvagers may find valuable intact plates, but the creature's feeding ground can be left dangerously cold or destabilized.

“Its intact plates are said to outweigh an entire crew's haul.”
From its lore

Variants

Small Lot: A lesser Brineweight with 180 Hit Points, CR 12 (8,400 XP), and no Ley-Surge.
Corrupted Ley: Its seams glow sickly green. Spells cast within 60 feet have a 25 percent chance of failing, at the DM's discretion. This is a custom variant effect.

Hooks

Plot hooks

A salvage crew offers a fortune for one intact plate, but the Brineweight's feeding ground is the only heat source keeping a nearby route open.
A pressure-sealed station reports violent tremors whenever the Brineweight shifts below it, and asks the party to drive it away without damaging the vents.
The creature has gathered around a newly active siphon site, where its presence may be a symptom of deeper disturbances rather than their cause.

How to use it

Use it as a dangerous obstacle in a narrow trench route, where escaping its reach requires navigating ledges, vents, or flooded passages.
Make the encounter a rescue or redirection problem rather than a simple fight, with nearby crews or settlements dependent on the same geothermal flow.
Use the Brineweight to introduce the risks of siphon activity or unstable ley energy without resolving the larger mystery of the pulse.
A calm approach can avert combat, while an assault may turn the surrounding terrain into a hazard of steam, heat, and collapsing basalt.

Treasure

An intact pressure plate may be valuable to salvage crews, but removing it can disrupt the local vent system.
The vent basin may contain abandoned extraction tools, pressure-sealed salvage, or records of earlier siphon operations.

Media

0 images

No images yet.

Visual sheet

Turn Brineweight into a sheet

A high-res, share-ready sheet you can post or print.