Glimmerfly Swarm

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Image promptlarge swarm of tiny glowing fey sprites, moth and dragonfly wings, thumb-sized luminous insects, churning ogre-sized cloud, self-shed cold bright light in blue violet and sickly green, blinding flare at its heart, corrupted Feywild thicket at night, twisted luminous fungi, black trees, long moving shadows, wide swarm composition, radiant against darkness, dark fantasy, grimdark, painterly digital art, dramatic chiaroscuro lighting, muted desaturated palette with corrupted-crimson accents, weathered post-Cataclysm atmosphere, intricate high detail, cinematic composition

Large Swarm of Tiny Fey, Chaotic Neutral

CR 3ControllerForest / Feywild

AC 13

HP 58 (13d10 − 13)

Speed 5 ft., Fly 40 ft. (hover)

STR

−3

save −3

DEX

save +5

CON

−1

save −1

INT

−2

save −2

WIS

save +2

CHA

save +3

Resistances Bludgeoning, Piercing, Slashing

Immunities Charmed, Frightened, Grappled, Paralyzed, Petrified, Prone, Restrained, Stunned

Senses Darkvision 60 ft.; Passive Perception 12

Languages —

Traits

Swarm. The swarm can occupy the space of a Tiny creature. It can't use or carry equipment.

Dazzling Aura. Every enemy who starts its turn within 10 feet of the swarm makes a DC 13 Constitution save. Failure: Its attack rolls have Disadvantage until the end of its next turn (the lights confuse its eyes).

Illumination. The swarm sheds 20 feet of Bright Light and an additional 20 feet of Dim Light.

Actions

Bewildering Motes. Melee Attack Roll: +5, reach 0 ft. (within the swarm's space). Hit: 14 (4d6) Psychic damage while the swarm's HP is above half; 7 (2d6) Psychic damage while its HP is at or below half.

Blinding Cloud (Recharge 4–6). The swarm suddenly flares. Every enemy who can see the swarm and is within 30 feet makes a DC 13 Constitution save.

Failure: Blinded for 1 minute. The target can repeat the save at the end of each of its turns.
Success: Attack rolls have Disadvantage until the end of its next turn.

Bonus Actions

Scatter and Reform. The swarm spends half its movement to move without provoking Opportunity Attacks. When it does so, each enemy whose space it passes through makes a DC 13 Dexterity save; on a failure it takes 3 (1d6) Psychic damage.

How to Use

The Glimmerfly Swarm controls sight. A blinded party loses the fight.

Feywild theme: These look like "cute fey lights." The party finds them pretty. Then Blinding Cloud hits.

Critical point: The swarm has Illumination — meaning the party will see it in the dark. This is deliberate: the swarm doesn't hide itself, it blinds with its own light. An inescapable threat, not a hidden one.

Combination:

Glimmerfly Swarm (Controller) + Lurker

The swarm blinds the party. A blinded party can't see the Lurker at all — the ambush works 100% of the time.

This is the best example of how a Controller and a Lurker can multiply each other's effect.

How the party wins: Area damage (swarms are weak to AoE — no Resistance!), Blindsight/Tremorsense, or closing their eyes and accepting the blindness (if you're going to be Blinded anyway, learn to fight Blinded).