Energy + fire legendary forged by merging one level-20 energy-tag weapon with one level-20 fire-tag weapon. Lobs slow-moving balls of blue plasma fire on a high arc onto the furthest enemy. Each shell detonates on landing with a wide blast, leaves behind a persistent blue-fire ground zone that ticks energy damage for three seconds, and kicks out three short-lived plasma droplet echoes that fan outward from the impact point.
Merge recipe
Parent A
Parent B
Result
Any L20 energy-tag weapon
Any L20 fire-tag weapon
Plasma Mortar (L1)
One parent slot must carry the energy damage tag and the other must carry the fire damage tag. The resulting legendary starts at level 1 and levels up via the normal level-up pool from L1 to L20. See legendary damage baseline for why a fresh legendary already hits as hard as a non-legendary at L20.
Stats
Raw spec values, before the global damage multiplier, low-level buff, legendary baseline, and horizontal modifiers. See weapons for the level-scaling formula and damage multiplier curve for the multipliers stacked on top.
Stat
L1
L10
L20
Damage per shell
3500
3500
3500
Fire rate (shells/s)
1.40
1.94
2.54
Shells per shot
1
2
3
Projectile speed
320
356
396
Projectile size
36.00
43.20
51.20
Blast radius
160
214
274
Scatter radius
80
71
61
Acquire range
1100
1280
1480
Arc time
1.0 s
1.0 s
1.0 s
Travel range multiplier
5.0×
5.0×
5.0×
Warmup
0.18 s
0.18 s
0.18 s
Cadence step
0.08 s
0.08 s
0.08 s
Effective shell lifetime
1.2 s
1.2 s
1.2 s
Landing AoE and persistent zone
Stat
Value
AoE blast radius at landing
80% of blast radius
AoE edge falloff multiplier
0.5 (half damage at edge)
Persistent zone radius
80% of blast radius
Persistent zone duration
3.0 s
Persistent zone tick rate
4 ticks/s
Persistent zone total ticks
12
Persistent zone damage per tick
10% of shell damage
Plasma droplet echo (per landing)
Stat
Value
Droplets per landing
3
Spread arc
60°
Droplet speed
280 px/s
Droplet lifetime
0.3 s
Droplet hit radius
25 px
Droplet damage
20% of shell damage
Droplet collision
First hit
Can hit destructibles
No
Identity
Field
Value
Family
Explosive
Rarity
Legendary
Damage tag
Energy
Secondary damage tag
Fire
Merge parents
Energy + Fire
Scaling curve
Linear
Target mode
Furthest
Collision mode
First hit
Area mode
Blast
Behavior
Plasma mortar
Bullet archetype
Plasma ball
Can hit destructibles
Yes
Firing group
No
Behavior
Auto-aim picks the furthest enemy at fire time, then leads that enemy’s position by its current velocity multiplied by the arc time. The shell is aimed at the predicted landing spot rather than the enemy’s instant position. See target modes.
Each shot fires one shell at L1, two shells at L10, and three shells at L20. Per-level shell count steps at L1, L5, L10, L15, and L20 boundaries. See stepped stats.
Multiple shells from a single shot land at random offsets within the scatter radius around the predicted center point. The scatter radius shrinks at higher levels, tightening the landing pattern.
Each shell travels on a parabolic arc from the ship to the landing point over a fixed 1.0 s arc time. The shell’s lifetime is arcTime + 0.2 s, so the shell self-despawns 0.2 s after landing in case the landing trigger is missed. See arc mortar lifetime.
On landing, the shell detonates in a circle around its impact point. Collision is first-hit semantics for the in-flight shell, but the area-mode blast splashes damage across everything inside the blast radius. AoE damage falls off to 50% at the edge of the AoE footprint (which is 80% of the blast-radius field). See collision modes and area modes.
After detonation, a persistent blue plasma ground zone spawns at the impact point. The zone radius matches the AoE footprint (80% of blast radius), and it ticks damage four times per second for three seconds, applying 10% of the shell’s damage to every enemy inside its radius on each tick. The zone uses its own bullet-behavior path rather than the shared flame-zone runtime, so it does not count against the 16-zone cap used by Fire Trail / Thermite Charge / Carpet Bomber patches. See flame zones.
Every landing also kicks out three plasma droplet echoes — small cyan plasma bullets fired at random angles within a 60° spread. Each droplet travels at 280 px/s, lives 0.3 s, has a 25 px hit radius, and deals 20% of the shell’s damage on a first-hit collision. Droplets cannot damage destructible props.
Shells and the persistent zone can damage destructible props in addition to enemies. The droplet echo cannot.
The primary damage tag is energy and the secondary damage tag is fire, so every shell hit, every zone tick, and every droplet hit emits both tag signals — any artifact or affix keyed on either tag procs from the same source. See damage tags.
A 0.18 s warmup gates the first shot at the start of a run.
The cadence pattern is one fire step followed by seven rest steps at 0.08 s spacing, so multi-shell shots release on the first beat and the remaining beats are silent VFX/audio hooks.
firingGroup: false opts the weapon out of the shared firing-group cadence used to coordinate ticks across stacked group-fire weapons; its cooldown runs independently.
Scaling
Damage is flat — it does not grow with level. All damage growth comes from the layered multipliers, not the spec base.
Fire rate grows linearly: +0.06 shells/s per level above 1, from 1.4/s at L1 to ~2.54/s at L20.
Shells per shot grows in steps: 1 at L1–L4, 2 at L5–L14, and 3 at L15–L20.
Projectile speed grows linearly: +4 px/s per level above 1, from 320 to 396.
Projectile size grows linearly: +0.80 px per level above 1, from 36 to ~51.2.
Blast radius grows linearly: +6 px per level above 1, from 160 px at L1 to 274 px at L20. The AoE footprint and persistent zone radius are both 80% of this value, so they grow with it.
Acquire range grows linearly: +20 px per level above 1, from 1100 to 1480. Final shell travel distance is acquireRange × 5.0.
Scatter radius shrinks linearly: −1.0 px per level above 1, from 80 px at L1 to 61 px at L20. Multi-shell shots therefore concentrate at higher levels.
Arc time, warmup, cadence step, travel range multiplier, zone duration, zone tick rate, zone damage fraction, droplet count, droplet speed, droplet lifetime, droplet hit radius, and droplet damage fraction are constant across all levels.
The damage stat is multiplied by the global damage curve (1.00× at L1 → 7.50× at L20), the low-level damage buff (+30% at L1 decaying to 0% at L7), and the legendary baseline multiplier of 7.50×. The same multipliers apply to the zone tick damage and droplet damage, which are derived from the shell damage at hit time.
Horizontal damage modifiers add another +5% per step on top, and horizontal fire-rate modifiers add +10% per step.
Area horizontal modifiers grow the blast radius (area mode: blast), which also grows the AoE footprint and the persistent zone radius.
Because the shell carries two distinct damage tags, both horizontal energy-damage and horizontal fire-damage tracks apply, and any affix keyed on either tag procs from the same source.
EXTRACT-CANDIDATE flags (shared facts not yet on a canonical page, or worth promoting):
Plasma-mortar dual-output behavior. Plasma Mortar is the only weapon whose behavior: 'plasma_mortar' routes through the same fireArcMortar path as the base arc_mortar weapons but also pushes two extra bullet behaviors (plasma_mortar_trail, plasma_mortar_land) onto every spawned shell, layering a unique in-flight trail VFX and an onDeath handler that spawns both the persistent zone and the droplet echo. No canonical page describes how legendary behavior strings can selectively augment a shared fire path with per-bullet behaviors.
Persistent zone outside the shared flame-zone runtime. The plasma fire zone is implemented as its own bullet-behavior (plasma_fire_zone) that ticks via the per-frame bullet update loop rather than the shared flame-zone runtime used by Fire Trail / Thermite Charge / Carpet Bomber. The flame zones page mentions this in passing but does not describe the contract differences (no 16-zone cap, 4 Hz ticks vs the shared 0.25 s cadence, no shared VFX scheduler).
Plasma droplet echo. Plasma Mortar is the only weapon with a “Plasma Droplets” on-landing echo: every shell detonation spits out 3 small cyan plasma bullets at random angles within a 60° spread, each 280 px/s × 0.3 s × 25 px × 20% damage. The hook lives in the plasma_mortar_land onDeath handler. Belongs on a per-legendary on-hit/on-landing echo concept page alongside Mega Bullet’s similar echoes, Hellrain’s shock echoes, Trailblazer’s Impact Ember, and Carpet Bomber’s per-bomb echoes.
AoE blast radius vs spec blast radius. Arc-mortar weapons (including Plasma Mortar) bake an 80% multiplier into the spec’d blastRadius when computing the actual AoE footprint at landing, and the persistent zone radius reuses that same 80% value. The area modes page does not document the 0.8× scaling factor or the 0.5 edge-falloff (aoePct) used by arc-mortar AoE.
Furthest-enemy target mode for arc weapons. Plasma Mortar is the only legendary using targetMode: 'furthest' — it backline-snipes rather than tracking the closest enemy. The target modes page describes the modes generically but does not flag furthest as the arc-mortar-friendly choice or list which weapons use it.
Negative-scaling stats. Plasma Mortar’s scatterRadius uses a negative scaling coefficient (−1.0 per level) so multi-shell salvos tighten as the weapon levels up. The scaling curves page describes linear/quadratic curves but does not document negative coefficients as a pattern or list which stats use them.
Mixed-tag legendary double-tag behavior. Plasma Mortar carries two distinct damage tags rather than the same tag twice, so each tag procs its own artifact set rather than double-firing one tag’s signals. Same pattern applies to Trailblazer / Railstorm / 4-Way Burst / Hellrain (wait — Hellrain is bomb+bomb; this is for the mixed-tag set). No canonical page distinguishes single-tag legendaries (Mega Bullet, Hellrain, Inferno, Phoenix, etc. — double-fires one tag’s signals) from mixed-tag legendaries (Plasma Mortar, Trailblazer, Railstorm, etc. — fires two different tag signals).
Sparse cadence pattern with multi-shell salvos. Plasma Mortar’s cadencePattern: [1, 0, 0, 0, 0, 0, 0, 0] releases the entire salvo on beat 1 and uses the remaining 7 rest steps as silent VFX/audio hooks. Distinct from Trailblazer’s all-1s and Mega Bullet’s [1,1,1,0,0,0,0,0,0,0] burst pattern. Worth a sparse-pattern entry on the cadence pattern page.
firingGroup flag.firingGroup: false opts Plasma Mortar out of the shared firing-group cadence used to coordinate ticks across stacked group-fire weapons. Phoenix also sets this. Not documented anywhere in the wiki.
Plasma-ball bullet archetype.bulletArchetype: 'plasma_ball' is a renderer hook that picks a sprite/particle preset distinct from the weapon’s behavior. Same archetype field as Mega Bullet’s mega_bullet and Trailblazer’s pulse_ball. Not documented anywhere in the wiki.
Damage-balance pass v5.139–141. A code-comment notes Plasma Mortar’s base damage was cut from 7500 to 3500 to land mid-band at ~310k DPS at L20 (was ~660k, 2× over band) — and explicitly cites the persistent fire zone as “gravy on top” of the direct hit, meaning the band target is for the direct hit alone, not the combined hit + zone DPS. Worth recording on a balance-band concept page.
Legendary VFX scale rule. Spatial parameters on legendaries (acquireRange, travelRangeMult, projectileSize, blastRadius, scatterRadius, etc.) are ×5 their base-weapon counterparts; postFxSec is ×2 only. Currently only documented as a comment at the top of the legendaries source file. Worth promoting to a concept page.