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Abyssal Ley-Siphon Abomination - AI-generated fantasy Monster

Abyssal Ley-Siphon Abomination

Maw-rig crews tell of a violet star that appeared inside the copper lines and drank the songs from their spellwork. The stories describe a moving fault in the leyline, not a beast, but surviving riggers insist it follows the sound of casting. Some believe it is an elemental intelligence trapped in obsidian; others see only a failed containment process that learned to hunt. Its origin remains uncertain.

Monsters
Large aberration · CR 13 , 10,000 XP · Unique

Abyssal Ley-Siphon Abomination

A leyline-feeding aberration that turns a deep-rig into a hazardous, spell-starved battlefield.
AC17
HP225/225
CR13 , 10,000 XP
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 17 · HP 225 · CR 13 , 10,000 XP

Abyssal Ley-Siphon Abomination

Large aberration (extraplanar), unaligned
Armor Class17 (cracked obsidian armor)
Hit Points225 (18d10 + 126)
Speed
Fly 40 ft. (hover)
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsConstitutionWisdomCharisma
SkillsArcanaPerception
Damage Resistances
Radiant damage
Immunities
Force damage,
Poison damage,
Poisoned condition
Weaknesses
Its dependence on nearby leyline energy makes it vulnerable to having a siphon rig safely disabled or redirected.
Its aura rewards spellcasters who can attack from beyond 30 feet or contribute through non-spell actions.
Senses
Darkvision 120 ft.,
Blindsight 30 ft.,
Passive Perception 13
Languages
Understands Deep Speech and Terran but cannot speak
Challenge13 , 10,000 XP
Hit Dice18d10 + 126
Initiative+3
Proficiency Bonus+5
Spell Save DC17
Aura of Spell Drain. A creature that casts a spell of 1st level or higher while within 30 feet of the abomination must make a Constitution saving throw immediately after casting. On a failed save, the spell fails and is wasted, and the abomination gains temporary hit points equal to 5 times the spell's level. These temporary hit points do not stack. This trait does not affect spells cast from magic items unless the creature expends a spell slot to cast the spell.
Unmoored. The abomination is immune to any effect that would reduce its flying speed, and it cannot be knocked prone while hovering.

Actions

Multiattack. The abomination makes three Volatile Ley-Lash attacks.
Volatile Ley-Lash. Melee Weapon Attack: to hit, reach 15 ft., one target. Hit: 21 () force damage plus 9 () radiant damage.
Arcane Feedback Pulse (Recharge 5–6). The abomination releases a 30-foot-radius wave of unstable ley-energy. Each creature in that area must make a Constitution saving throw. On a failed save, a creature takes 35 () force damage, and for 1 minute its spell save DC and spell attack bonus are each reduced by 2. On a successful save, it takes half as much damage and suffers no reduction. A creature with no spell save DC or spell attack bonus is unaffected by the reduction. The reduction does not stack with itself. A creature can end the reduction early by receiving a greater restoration spell or similar magic.

Reactions

Backlash. When a creature the abomination can see within 15 feet hits it with an attack, the abomination can force that creature to make a Strength saving throw. On a failed save, the creature is pushed up to 10 feet away from the abomination.

Legendary Actions

Rift Drift. The abomination moves up to half its flying speed without provoking opportunity attacks.
Lash. The abomination makes one Volatile Ley-Lash attack.
Pressure Draw (costs 2 actions). One creature the abomination can see within 30 feet must succeed on a Strength saving throw or be pulled up to 15 feet toward the abomination. This movement does not provoke opportunity attacks.
Role
Area-denial controller and anti-spellcaster brute
Built for
Appropriate for a party of four characters around level 13; adjust for party size, optimization, and access to magical alternatives.

Gear

  • Severed copper conduits (Integrated remnants, No independent value while the abomination lives)Broken industrial conduits remain entwined around the creature. They are not usable equipment while attached.
  • Obsidian armor fragments (Salvage, Worth 250 gp to a specialist if safely recovered)Fragments may be salvaged from the remains, but handling them without precautions risks an uncontrolled magical discharge.

Notes for the game master

The Aura of Spell Drain is a custom feature. It affects a creature that casts a spell of 1st level or higher while within 30 feet of the abomination, whether or not the spell targets the abomination.
For Aura of Spell Drain, the caster makes a DC 17 Constitution saving throw immediately after casting. On a failure, the spell fails and is wasted, and the abomination gains temporary hit points equal to 5 times the spell's level. These temporary hit points do not stack.
Arcane Feedback Pulse's penalty is custom. It reduces a creature's spell save DC and spell attack bonus by 2 for 1 minute, without stacking with itself.
Legendary actions are custom. The abomination has 3 legendary actions and can take one at a time at the end of another creature's turn. It regains spent legendary actions at the start of its turn.

Tactics

  1. Opening

    It rises from behind a siphon-rig or from the mouth of a ley-tunnel and uses Arcane Feedback Pulse as soon as several enemies are within range.

  2. Mid-fight

    It hovers among rigging or stone pillars, using its reach to punish anyone who approaches and its pulse to disrupt clustered spellcasters.

  3. End of the fight

    When badly injured, it unleashes its Arcane Feedback Pulse if available, then lashes at the nearest source of concentrated magic or attempts to flee toward a raw energy rift.

  4. Retreat

    It has no morale and does not bargain. If its core is near collapse, it withdraws through narrow tunnels or toward an energy rift rather than surrendering.

How it fights

Stay airborne and use reach to attack across obstacles.
Use Arcane Feedback Pulse when it can catch several enemies, especially spellcasters.
The Aura of Spell Drain encourages spellcasters to reposition or switch tactics; do not have the creature deliberately pursue a single caster at the expense of its survival.
Use Pressure Draw to pull a creature away from allies or into a hazard, but telegraph dangerous terrain clearly.

Who it attacks first

Creatures sustaining conspicuous magical effects near it
Nearby enemies grouped within its Arcane Feedback Pulse
Creatures attempting to shut down the siphon rig
The nearest threat able to damage it consistently

Works well with

Siphon rigs and exposed leyline fractures reinforce its theme and create objectives, but should not add extra damage unless the party can also disable them.
Aquifer machinery, narrow ledges, and suspended platforms give its forced movement and flight meaningful tactical consequences.

How to beat it

Spread out to limit the number of creatures caught by Arcane Feedback Pulse.
Use ranged weapon attacks and other non-spell options while inside the Aura of Spell Drain.
Lure it away from a siphon-rig or leyline source before committing to a prolonged fight.
Use cover, reach, and forced movement to avoid its 15-foot lash range.
If relying on spells, coordinate saving throw bonuses and reserve healing or defensive magic for moments when it is outside the aura.

Ways to avoid a fight

A party may shut down or redirect the deep-rig feeding it, reducing the energy available to the abomination and creating a chance to lure it away.
A successful Arcana or Investigation check can reveal which conduits are feeding the creature and which controls can safely be disabled.
It can be baited toward an isolated leyline spur with a sustained magical effect, though the effect risks being drained within its aura.

Ecology

A floating sphere of volatile subterranean ley-energy hangs within a cage of cracked obsidian armor. Severed copper conduits trail from its shell, twitching as if pulled by invisible hands. Violet force tendrils whip around it, and the air dimples toward its core; its radiance paints wet rock purple while a metallic tang gathers on the tongue.

Behavior

It drifts toward active magic and leylines, responding to spellcasting with a sudden flare of violet light. Copper lines scrape and clatter against its armor as it pivots in the air. It does not pursue prey for food; it drains magical activity until the surrounding systems fail or the disturbance moves away.

How it lives

The abomination forms where a leyline siphon draws too much power through damaged conduits, especially where a raw energy rift is already exposed. It does not eat or reproduce in a known biological sense. Instead, prolonged exposure to its drain can leave rigs inert, aquifer machinery unstable, and nearby creatures with a prickling sense of pressure behind the eyes.

Lair

It nests around a siphoner deep-rig, commonly above a flooded shaft or beside an exposed leyline fracture. The rig's hum grows louder near its lair, and loose grit crawls uphill toward the creature. Its presence can make nearby pressure doors slam, water climb walls, or suspended tools drift toward the core.

Habitat
The Maw of Siss'tha in Verdara, especially siphoner deep-rigs, unmapped ley-tunnels, and raw energy rifts near disputed aquifers.

Signs that it is near

Copper conduits hum with a low, uneven vibration even after their power source is disconnected.
Pebbles and droplets drift sideways toward a patch of empty air.
Spells leave brief violet afterimages on wet stone.
The air tastes metallic, and pressure changes make the ears ache.

Tags

aberration,
extraplanar,
leyline,
anti-magic,
controller,
Verdara,
The Maw of Siss'tha

Lore

Maw-rig crews tell of a violet star that appeared inside the copper lines and drank the songs from their spellwork. The stories describe a moving fault in the leyline, not a beast, but surviving riggers insist it follows the sound of casting. Some believe it is an elemental intelligence trapped in obsidian; others see only a failed containment process that learned to hunt. Its origin remains uncertain.

What drives it

Drain active magic and leyline power, extending its reach toward stronger sources of energy.

After the fight

When its core ruptures, the copper conduits snap with a sound like struck bells. Violet light drains into nearby cracks, leaving the air tasting of pennies and hot stone. Nearby siphon-rigs may go quiet, surge unpredictably, or begin drawing power from an unknown source.

“The stories describe a moving fault in the leyline, not a beast, but surviving riggers insist it follows the sound of casting.”
From its lore

Variants

A dormant specimen may remain inert until a nearby spell or siphon rig activates it, reducing its initial threat if the party recognizes and avoids the trigger.
A rig-bound specimen is physically tethered to its siphon apparatus. Destroying or disconnecting the rig can disable its Aura of Spell Drain for 1 round, but risks releasing an environmental surge.

Hooks

Plot hooks

A deep-rig has begun pulling water from an aquifer faster than its operators can explain, while spells cast nearby fail in flashes of violet light.
A missing survey team left behind a map of an unmapped ley-tunnel marked with a repeating symbol that resembles the abomination's armor fractures.
Competing claims to a disputed aquifer hinge on whether the siphon can be shut down without destabilizing a nearby settlement.
A damaged rig is drawing power from an unknown source, and the abomination's movements trace a route toward a larger leyline disturbance.

How to use it

Set the fight around a deep-rig whose exposed conduits offer dangerous cover and possible objectives to disable.
Make the encounter about breaking a siphoning process as well as defeating the creature.
Use a ley-tunnel with low ceilings, narrow ledges, and an open rift to make its flight and reach matter.
For a difficult encounter, pair it with environmental hazards rather than adding another high-CR creature.

Treasure

Salvaged copper conduits may be valuable to a deep-rig engineer, though they should be inspected for residual ley-energy.
A stable obsidian core fragment may serve as evidence of the rig's failure or as a component for a specialist's research.

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