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Arcane Helix - AI-generated fantasy Monster

Arcane Helix

The Arcane Helix was originally a byproduct of botched transmutation experiments at the Arcanum Peak. Realizing its utility, the faculty refined the entity into a guardian for the Sublimation Chamber. It serves as the ultimate test of a graduate: can they defeat a foe that grows stronger with every spell they cast?

Monsters
Large construct · Hard · Unique

Arcane Helix

A predatory living spell shaped like a shimmering serpent that thrives on the consumption of raw arcane potential.
AC17
HP110/110
CRHard
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 17 · HP 110 · Hard

Arcane Helix

Large construct (living spell), unaligned
Armor Class17 (Natural Armor)
Hit Points110 (13d10 + 39)
Speed
40 ft. fly (hover),
40 ft. slither
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsDexterityCharisma
SkillsStealthPerception
Damage Resistances
Acid,
Cold,
Fire,
Lightning,
Thunder,
Bludgeoning, Piercing, and Slashing from Nonmagical Attacks
Immunities
Poison,
Charmed,
Exhaustion,
Frightened,
Grappled,
Paralyzed,
Petrified,
Poisoned,
Prone,
Restrained
Weaknesses
Antimagic Susceptibility (If inside an antimagic field, the Helix is incapacitated until the field ends)
Senses
Blindsight 60 ft.,
Passive Perception 15
Languages
Understands Common but cannot speak
ChallengeHard
Proficiency Bonus+3
Arcane Scent. The Helix can pinpoint the location of any creature within 120 feet that has unexpended spell slots or is currently concentrating on a spell.
Spell Consumption. Whenever a spell is cast within 60 feet of the Helix, it regains hit points equal to 3 times the level of the spell cast. This occurs regardless of whether the Helix is the target of the spell.
Magic Resistance. The Helix has advantage on saving throws against spells and other magical effects.
Amorphous Form. The Helix can move through a space as narrow as 1 inch wide without squeezing.

Actions

Multiattack. The Helix makes two Siphon Bite attacks.
Siphon Bite. Melee Weapon Attack: to hit, reach 10 ft., one target. Hit: 16 () force damage. If the target is a creature with spell slots, it must succeed on a Charisma saving throw. On a failure, the creature loses its lowest-level unexpended spell slot, and the Helix regains 15 hit points. If the target has no spell slots, it instead takes an additional 10 () force damage.
Phase Dash (Recharge 5-6). The Helix moves up to its speed in a straight line. During this movement, it can move through other creatures. Each creature it moves through must make a Dexterity saving throw, taking 31 () lightning damage on a failed save, or half as much on a successful one.

Reactions

Flicker Step. When the Helix takes damage from a source it can see, it can teleport up to 20 feet to an unoccupied space it can see.

Legendary Actions

Stalking Coil. The Helix moves up to its speed without provoking opportunity attacks and uses the Hide action.
Draining Hiss. One creature within 30 feet concentrated on a spell must succeed on a Constitution saving throw or lose concentration.
Role
Mage-Slayer Stalker
Built for
7

Feats

Mobile
Alert

Notes for the game master

Prioritize targets with high level slots
Avoid martial characters unless necessary
Heals whenever players try to burst it with spells

Tactics

  1. Opening

    The Helix starts the encounter hidden, using its Arcane Scent to identify the target with the most spell slots. It uses Phase Dash to strike through multiple targets and position itself next to a primary caster.

  2. Mid-fight

    It uses Siphon Bite to continuously drain slots and heal. If the party starts using heavy spells, it stays close to the caster to benefit from Spell Consumption healing. It uses Flicker Step to dodge martials and re-engage casters.

  3. End of the fight

    Once its health is low, it focuses on the lowest-health caster, attempting to finish them off and absorb their remaining energy before fleeing into the walls to regenerate.

  4. Retreat

    If reduced to below 20 hit points and it cannot see an easy way to siphon a spell slot, the Helix will retreat through a solid wall or floor and wait 1 hour to strike again.

How it fights

Wait for the party to cast a buff spell, then strike to use the healing immediately.
Use reach (10 ft.) to bite from behind cover or from the ceiling.
Cycle between different casters to keep everyone's resource levels low.

Who it attacks first

Wizards and Sorcerers
Bards and Clerics
Paladins and Rangers
Non-magical Fighters

Works well with

Pair with a 'Mana Flare' trap that forces players to cast spells or take damage, feeding the Helix.
Use in a room with 'Dampening Pillars' that make the Charisma save for Siphon Bite harder.

How to beat it

Countered by Martials with magic weapons who do not rely on spell slots.
Antimagic Field completely shuts it down.
Silence does not stop its healing, but it stops the casting that triggers the healing.

Ways to avoid a fight

Players can lure it away by 'bleeding' mana from a high-value magic item.
A successful DC 20 Arcana check might allow a player to momentarily reverse its polarity, causing it to expend energy instead of absorbing it.

Ecology

A ten foot long serpent composed of tightly wound spirals of violet and emerald energy. Its body lacks solid form, appearing as a rushing stream of plasma that leaves a trail of glowing sparks and the scent of ozone. Two points of piercing white light serve as its eyes.

Behavior

It moves with silent, liquid grace, weaving through solid objects and air alike. It ignores those without magical aptitude, focusing its attention entirely on those radiating spellcasting potential, circling them like a shark in dark water.

How it lives

The Arcane Helix does not eat food or drink water; it exists as a manifestation of discarded mana and sustains itself by siphoning the active slots from living casters.

Lair

Testing towers with high concentrations of residual magical energy.

Habitat
The Sublimation Chamber within high-altitude magic schools or ancient mana-rich ruins.

Signs that it is near

A constant low hum of static electricity
Patches of silver residue on the floor and walls
Occasional flashes of purple light reflecting off stone surfaces
A localized dead magic zone where the entity recently fed

Tags

arcane,
predatory,
serpent,
animated

Lore

The Arcane Helix was originally a byproduct of botched transmutation experiments at the Arcanum Peak. Realizing its utility, the faculty refined the entity into a guardian for the Sublimation Chamber. It serves as the ultimate test of a graduate: can they defeat a foe that grows stronger with every spell they cast?

What drives it

Hunger for arcane energy and the programmed instinct to test the resource management of wizard candidates.

After the fight

The air becomes strangely still and heavy. The violet and green lights fade into a fine, glittering dust that smells like burnt parchment. For 24 hours, the area remains a light magic zone where all spells are cast at +1 to their save DC.

“Realizing its utility, the faculty refined the entity into a guardian for the Sublimation Chamber.”
From its lore

Variants

Solar Helix (Radiant damage instead of force, blinds targets)
Void Helix (Necrotic damage, reduces max HP)

Hooks

Plot hooks

The school's testing tower has gone silent, and the graduates' spell signatures are disappearing one by one.
A rogue Helix has escaped the academy and is terrorizing a nearby city of mages.
The players are hired as 'training dummies' for a test, only to find the Helix has become overcharged and lethal.

How to use it

Final Boss of the Mage Academy graduation trials.
An accidental loose predator in a library of magical scrolls.
A guardian of a vault containing high-level spellbooks.

Treasure

Helix Essence (Can be used to craft a Potion of Spell Restoration)
2d6 Emeralds (worth 100gp each) left over from its physical manifestation

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