Killchain Coil

What it is

A stat-category artifact built around a kill counter. Every N enemy kills, the coil discharges: weapons surge with bonus damage for a few seconds AND a circular shockwave around the ship deals flat damage to nearby enemies on the same instant. The kill counter resets after each proc, so procs are paced by enemy throughput rather than a wall-clock cooldown.

Identity

Field	Value
Display name	Killchain Coil
Category	Stat
Icon	🎯
Primary color	ffaa00
Secondary color	cc6600
Bright/highlight color	ffdd66
Damage tag	None (type-agnostic)
Proc audio cue	Flavored cue plays on every discharge (routed through the game audio bus with low-pass and reverb, treated as a spatial world event).
Passive flat bonus	Weapon Damage (applied as a flat additive percent, scaling by tier per the engine-wide flat-bonus table).

Per-tier values

Tiers are indexed by rarity. The four authored tiers cover uncommon through legendary; the runtime prepends a fifth “common” tier that reuses the uncommon row’s values and differentiates only through the smaller passive flat bonus.

Rarity	Kill threshold (kills per proc)	Weapon damage surge (flat % added to weapon damage)	Surge duration (seconds)	Discharge-ring damage (flat per proc)
Common	30	+40%	5	30
Uncommon	30	+40%	5	30
Rare	25	+60%	5	45
Epic	20	+90%	6	65
Legendary	15	+140%	6	90

Effect

Trigger: counter-based. The artifact subscribes to the enemy-kill signal and increments an internal counter. When the counter reaches the tiered threshold it fires, then resets to zero.

Action	Effect
Weapon-damage surge	Adds the tiered flat percent to weapon damage for the tiered duration. The source tag is the artifact’s own id, so the engine refreshes a single instance rather than stacking additional copies.
Discharge-ring hitbox	Spawns a secondary area-of-effect hitbox centered on the ship with a 220-pixel radius, dealing the tiered flat damage to any enemy inside. Resolves on the same frame as the proc.
Visual burst	Plays a burst-and-ring VFX in the artifact’s bright color (20 particles, scale 5.0, lifetime 0.40 s).
Artifact flash	Flashes the artifact’s HUD icon to signal the proc.
Banner	Shows the artifact’s banner the first time it procs in a run.

The damage surge and the discharge ring fire from the same trigger, so each proc is both a stat buff window and an immediate AoE damage event.

Stacking rules

Rule	Behavior
Max stacks	1
Stacking mode	Refresh — a fresh proc replaces the existing weapon-damage surge, resetting its remaining duration to the full tiered value.
Modifier source	artifact:killchain_coil (used to find and refresh the existing surge instead of adding a second copy).
Counter reset	The kill counter resets to zero after each proc, so it must be filled again from scratch. Kills outside the active surge window still count toward the next proc.
Discharge ring stacking	The AoE hitbox is a one-shot per proc — it does not persist between procs, so it neither stacks nor refreshes.
Pacing	With no wall-clock cooldown, proc frequency depends entirely on kill rate vs. threshold. Lower thresholds at higher tiers shorten the time between procs in dense fights.

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Summary: Killchain Coil is a stat artifact whose proc fires every N kills, granting a refresh-stacked weapon-damage percent surge plus a 220-pixel discharge ring around the ship that deals flat damage in a single frame. Kill threshold scales 30 → 15, surge magnitude scales +40% → +140%, surge duration scales 5 s → 6 s, and ring damage scales 30 → 90 across common/uncommon → legendary. Common reuses uncommon’s values per the shared-tier convention. Each proc plays a flavored audio cue.

EXTRACT-CANDIDATE flags:

• The “fifth common tier reuses uncommon’s values and differentiates only via the flat passive bonus” rule is shared across all artifacts and belongs on the artifacts roll-up page, not repeated per entity.
• The engine-wide flat-bonus tier table (10 → 50 across common → legendary, applied to whatever stat the artifact maps to) is shared infrastructure and belongs on the artifacts overview or authoring guide.
• The counter trigger semantics (subscribes to a signal, increments, resets on threshold) are a generic effect-engine concept; canonical definition belongs on a combat or effect-engine page.
• The modify_stat, damage_aoe, vfx, flash_artifact action types are shared primitives across many artifacts — canonical reference belongs on the artifact authoring guide.
• The stacking: 'refresh' / maxStacks modifier semantics are generic effect-engine behavior and belong on the same shared reference.
• The proc-audio-cue routing rule (game bus, low-pass + reverb, treated as spatial world event, default silent when omitted) is engine-wide and belongs on the artifacts roll-up or an audio reference page.
• The 220-pixel discharge-ring radius reuses a value tuned originally for a separate prop — this cross-artifact “magnetar-tuned radius” convention is implementation lineage, not a per-artifact fact; if documented, it belongs on the authoring guide.