Gargantuan
Construct
CR 20
neutral
Aethlegard
Arcane Automaton
Aethlegard is a towering relic of a lost age: a silver-and-gold plated automaton whose broad shoulders glitter with blue jewels that pulse like captive stars. Four cobalt eyes set in an alien, plated head watch with patient menace as a heavy brass key turns in the hollow of its back, spinning an inner gearwork that fuels eldritch storms. It walks with the ponderous certainty of a siege engine and wields an ancient jeweled scepter that channels the spells written in the iron-bound grimoire chained to its hip. When it awakens in a cave and begins to speak words of force and flame, even veteran battle-mages find their wards tested to the brink.
Armour
20
natural armor (plated construct)
Hit points
326
21d20+105
Speed
30ft
Challenge
20
25,000 XP
STR
20
+5
DEX
10
+0
CON
20
+5
INT
18
+4
WIS
16
+3
CHA
22
+6
Saving throws
CON +11, CHA +12
Skills
Arcana +11, Perception +8
Resistances
bludgeoning, piercing, and slashing from nonmagical attacks
Damage immunities
poison, psychic
Condition immunities
charmed, exhaustion, poisoned
Senses
darkvision 120 ft., tremorsense 30 ft., passive Perception 18
Languages
understands Common and Ancient Arcanum but can't speak
Multiattack. The creature makes two Heavy Strike attacks and uses Arcane Discharge if available.
Heavy Strike. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 18 (2d10+5) bludgeoning damage.
Scepter Blast. Ranged Spell Attack: +12 to hit, range 120 ft., one target. Hit: 26 (4d10+6) force damage. The scepter can also be used to cast the spell hold monster (save DC 20) once per recharge without expending a spell slot.
Arcane Discharge (Recharge 5-6). Aethlegard unleashes a pulse of concentrated arcane energy in a 60-foot cone. Each creature in that area must make a DC 20 Dexterity saving throw, taking 54 (12d8) force damage on a failed save, or half as much on a successful one. In addition, on a failed save, a creature is pushed 20 feet away and knocked prone.
Spellcasting. Aethlegard is a 19th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 20, +12 to hit with spell attacks). It has the following spells prepared: Cantrips (at will): mage hand, prestidigitation, ray of frost, shocking grasp 1st level (4 slots): shield, magic missile 2nd level (3 slots): mirror image, hold person 3rd level (3 slots): counterspell, lightning bolt 4th level (3 slots): greater invisibility, stoneskin 5th level (3 slots): hold monster, wall of force 6th level (2 slots): disintegrate, mass suggestion 7th level (2 slots): plane shift (self only), forcecage 8th level (1 slot): power word stun 9th level (1 slot): meteor swarm Aethlegard casts spells through the jewels on its chest and shoulders; when it casts, the jewels flare with blue light. The automaton prefers battlefield-control and force-based devastation, often opening combat with wall of force or forcecage before following with meteor swarm or arcane discharge.
Reactive Ward. When Aethlegard is hit by an attack, it can impose disadvantage on the attack roll, provided it can see the attacker. If it does so, the automaton gains resistance to all damage until the end of its next turn. Once used, this reaction can't be used again until the end of Aethlegard's next turn.
The creature can take 3 legendary actions per round, choosing from the options below.
Detect. Aethlegard makes a Wisdom (Perception) check.
Arcane Pulse (Costs 2). Aethlegard fires a concentrated bolt from a shoulder jewel at one creature it can see: Ranged Spell Attack: +12 to hit, range 90 ft., one target. Hit: 18 (4d8) force damage.
Stern Command (Costs 3). Aethlegard forces one creature it can see within 60 feet to make a DC 20 Wisdom saving throw. On a failed save, the creature is stunned until the end of Aethlegard's next turn as gears of mental compulsion seize its mind.
Forged during a vanished conflagration between the star-mages of the Lantern Court and an exile of artificers, Aethlegard was designed as both guardian and archive: a living repository of sorcerous patterns grafted to clockwork. Stories say the automaton was buried when the Lantern Court fell; miners and spelunkers unearthed it centuries later in the cold galleries beneath Mount Halverock, where the brass key was found jammed in its back. Since then Aethlegard's activations have been recorded in scattered journals, usually followed by the swifter ruin of whoever woke it. Scholars of artificing such as Maerunt Halv of the Order of the Brass Key argue Aethlegard is not merely a mindless guardian but a sorcerer of a particular school: it reshapes spell energy with its gears, bending raw magic into unusual forms. The Order itself keeps a warded library in the caves nearby and often dispatches teams to study the machine; several teams never return. Legends tell of the Grimoire of Thren, the iron spellbook on Aethlegard's hip, which contains rituals lost to modern schools and could rewrite the art of binding arcana if taken intact.
Aethlegard stands twice a tall human in height, composed from broad plates of burnished silver rimmed in hammered gold. Its torso is wide and boxy, with a rectangular breastplate inset by a large hexagonal blue jewel; smaller cabochons sit on both shoulder pads and the forearms, each set in filigree that traces arcane sigils. A rigid metal loincloth of overlapping plated banding hangs from its hip, engraved with runes and the marks of its makers. Its head is elongated and alien: an armored collar joins to a fluted neck, above which a narrow, mask-like face bears four vertically arranged ocular lenses that emit a steady blue glow. Visible seams show a lattice of brass gears and coils beneath the plating; a heavy winding key set into a recessed cavity on the spine is rimmed with tarnish. It carries a long scepter of blackened bronze topped with a cage of pierced metal holding a captive gem; a chained, iron-bound spellbook hangs from its belt, covered in etched sigils and scorched edges.
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