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Solarium Prime

Created during the First Age of Dawn by a sect of master solar-smiths, Solarium Prime was built to be the final word in defense. It is said that the 'Unextinguished Spark' it guards is a fragment of the sun's first rays, and the construct is bound to its heat and light.

Monsters
Huge construct · CR 21 · Unique

Solarium Prime

A solar-powered sentinel constructed from divine metals and enchanted mirrors, designed to guard the ultimate source of light.
AC22
HP362/362
CR21
Init
STR
DEX
CON
INT
WIS
CHA
ConditionsNone

Combat

AC 22 · HP 362 · CR 21

Solarium Prime

Huge construct (guardian), lawful neutral
Armor Class22 (Natural Armor)
Hit Points362 (25d12 + 175)
Speed
40 ft. walking,
40 ft. flying (hover)
STR
DEX
CON
INT
WIS
CHA
Saving ThrowsSTRCONWIS
SkillsPerceptionInsight
Damage Resistances
Fire,
Force,
Bludgeoning, Piercing, and Slashing from nonmagical attacks
Immunities
Radiant,
Poison,
Psychic,
Charmed,
Exhaustion,
Frightened,
Paralyzed,
Petrified,
Poisoned
Weaknesses
Vulnerability to Cold
Senses
Truesight 120 ft.,
Passive Perception 19
Languages
Celestial,
Common,
Telepathy 120 ft.
Challenge21
Proficiency Bonus+6
Illumination. Solarium Prime sheds bright light in a 60-foot radius and dim light for an additional 60 feet.
Immutable Form. Solarium Prime is immune to any spell or effect that would alter its form.
Legendary Resistance. If the construct fails a saving throw, it can choose to succeed instead (3/Day).
Reflective Surface. Any creature that starts its turn within 30 feet of the construct and can see it must make a Constitution saving throw or be blinded until the start of its next turn.

Actions

Multiattack. Solarium Prime makes three Searing Lance attacks.
Searing Lance. Ranged Weapon Attack: to hit, range 120 ft., one target. Hit: 30 () radiant damage. If the target is a creature, it must succeed on a Strength saving throw or be pushed 15 feet away.
Solar Flare (Recharge 5-6). Solarium Prime releases a wave of intense heat and light. Each creature in a 30-foot radius sphere centered on the construct must make a Constitution saving throw. A creature takes 70 () radiant damage on a failed save, or half as much damage on a successful one.

Reactions

Mirror Retaliation. When Solarium Prime takes damage from a spell, it uses its mirrors to catch the energy. The construct reduces the incoming damage by half. It then forces the caster to make a Dexterity saving throw. The caster takes the other half of the damage on a failed save, or half of that on a success.

Legendary Actions

Tactical Reposition. Solarium Prime moves up to its speed without provoking opportunity attacks.
Focused Beam. Solarium Prime makes one Searing Lance attack.
Blinding Pulse (Costs 2 Actions) (costs 2 actions). Solarium Prime emits a burst of light. Each creature within 20 feet of it must succeed on a Constitution saving throw or be blinded for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Role
Tank / Ranged Striker
Built for
17 to 20

Gear

  • Solarium Mirrors (Equipment, 100000 gp (for the set))Highly conductive crystal mirrors that integrate into the automaton's frame.

Feats

Sentinel
Great Weapon Master (Visual Reskin)

Augmentations

Crystalized Photovoltaic Core

Notes for the game master

Use Searing Lance for kiting and area denial.
Always save Legendary Resistances for crowd control spells.
Remember the cold vulnerability if the party has a Wizard.

Tactics

  1. Opening

    Starts the fight by flying to a high vantage point and using Solar Flare to thin out glass cannon PCs.

  2. Mid-fight

    Focuses Searing Lances on the strongest spellcasters to force concentration checks and uses Mirror Retaliation to punish damage-heavy spells.

  3. End of the fight

    Engages in melee if forced, using its high AC and Reflective Surface to outlast survivors.

  4. Retreat

    Does not retreat. It will fight until destroyed to protect the Unextinguished Spark.

How it fights

Keep out of reach using flight.
Target creatures with low Constitution saves.
Prioritize targets that use fire damage as it is resisted.

Who it attacks first

Clerics
Wizards
Archers

Works well with

Combine with light-based traps that deal radiant damage to recharge or buff the construct.
Works well with high-level Paladins or Celestial subordinates.

How to beat it

Cold damage spells like Cone of Cold.
Darkness spells (to negate Reflective Surface).
Anti-magic Field.

Ways to avoid a fight

Providing the 'Litany of the Sun' might allow peaceful passage.
Offering a gemstone of high clarity might distract the construct temporarily.

Ecology

A towering twenty-foot automaton forged from gleaming, polished gold and white marble. Its torso and limbs are covered in hundreds of articulating hexagonal mirrors that pulse with a rhythmic, golden internal light. Its head is a single massive, convex crystal lens that glows with the intensity of a trapped star.

Behavior

Solarium Prime remains perfectly motionless, indistinguishable from a statue, until its ward is approached. It speaks in a voice like vibrating glass, offering a single warning before engaging with calculated, efficient movements.

How it lives

As a construct, it does not eat or sleep. It sustains its core by absorbing ambient light through its mirrored plates, effectively serving as a permanent extension of the temple's security.

Lair

The Threshold of the Unextinguished Spark, a chamber designed to focus natural or magical light onto the automaton.

Habitat
Celestial temples, ancient desert ruins, or the heights of solar citadels.

Signs that it is near

Intense heat radiating from a distance
Blinding flashes of light reflecting off walls
Scorch marks on the floor leading to the entrance
The smell of ozone and molten metal

Tags

Sentinel,
Solar,
Legendary

Lore

Created during the First Age of Dawn by a sect of master solar-smiths, Solarium Prime was built to be the final word in defense. It is said that the 'Unextinguished Spark' it guards is a fragment of the sun's first rays, and the construct is bound to its heat and light.

What drives it

To prevent any being from touching or claiming the Unextinguished Spark without the proper ritual authorization.

After the fight

Once destroyed, the Unextinguished Spark is exposed. If the construct was the only thing containing the heat, the room may begin to melt, creating a chase sequence for the party to escape with their prize.

Variants

Lunar Guardian (deals Cold and Necrotic damage instead of Fire and Radiant)

Hooks

Plot hooks

The Unextinguished Spark is fading, and Solarium Prime has gone berserk, attacking nearby villages in search of light.
A rogue solar-smith asks the party to 'update' the automaton's mirrors.

How to use it

Final boss of a desert dungeon.
Guardian of a high-level magic item.

Treasure

Polished Gold Plating (worth 15,000 gp)
1d4 Solarium Shards (used to craft sun blades or radiant weapons)

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