What it is
A mini-boss is the encounter slotted into a “mini-boss” level. It is a full boss-pool encounter run at half-strength stats: the same authored boss roster, the same authored arena and abilities, but with HP and damage multipliers tuned down so the fight serves as a mid-run gate rather than the final wall of a run.
Mini-boss levels appear on a fixed cadence inside a run. Each one swaps biome world-gen for a sealed square arena, spawns one boss roster picked randomly from the same pool the final boss uses, and ends the level the moment the roster’s shared health bar empties. There is no time limit, no biome timer, no portal walk-through — the level is the fight.
The pool of bosses that can roll as a mini-boss is the same pool that can roll as the final boss. Every shipped boss is currently tagged for the mini pool; no boss is mini-exclusive.
Stats / variables tables
Run cadence
| Mode | Total levels | Mini-boss level slots | Final boss slot |
|---|---|---|---|
| Normal | 5 | level 3 | level 5 |
| Challenge | 10 | levels 3, 6, 9 | level 10 |
Per-level kind sequence
| Mode | L1 | L2 | L3 | L4 | L5 | L6 | L7 | L8 | L9 | L10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Normal | normal | normal | mini-boss | hard | boss | — | — | — | — | — |
| Challenge | normal | normal | mini-boss | normal | normal | mini-boss | hard | hard | mini-boss | boss |
Stat multipliers vs base authored stats
| Tier | HP multiplier | Damage multiplier | Reward chamber cascade rings |
|---|---|---|---|
| Mini-boss | 4.0 | 4.0 | 1 |
| Final boss | 8.0 | 8.0 | 2 |
Mini-boss HP and damage equal half of final-boss HP and damage for the same roster.
Depth ramp on top of the tier multiplier
| Position in run | Depth multiplier | Combined HP multiplier (mini) | Combined damage multiplier (mini) |
|---|---|---|---|
| First level of run | 1.00 | 4.00 | 4.00 |
| Final level of run | 1.50 | 6.00 | 6.00 |
| Normal mode L3 (mini-boss) | 1.50 | 6.00 | 6.00 |
| Challenge mode L3 (mini-boss) | 1.22 | 4.89 | 4.89 |
| Challenge mode L6 (mini-boss) | 1.56 | 6.22 | 6.22 |
| Challenge mode L9 (mini-boss) | 1.89 | 7.56 | 7.56 |
Depth ramp is 1.0 + 0.5 × (currentLevel - 1) / (totalLevels - 1), computed against the run’s total level count.
Mini-boss pool — which boss can roll, and its authored stats
| Boss | Arena shape | Arena size (world units) | Authored HP pool | Authored bar damage | Add-pressure profile | Roster body count |
|---|---|---|---|---|---|---|
| Killer Croc | circle | radius 350 | 6000 | from authored abilities | light_pressure | 1 boss + 4 anchors |
| Prism Cluster | circle | radius 400 | 6000 (4 × 1500) | from authored abilities | none | 4 gems |
| Junkrat Captains | rectangle | 700 × 500 | 6000 (3000 + 2 × 1500) | from authored abilities | heavy_pressure | 3 captains |
| Digbot Swarm | circle | radius 450 | 6000 (100 × 60) | from authored abilities | none | 100 |
| Awakened Mech | circle | radius 380 | 8000 (single bar, body swaps) | from authored abilities | crescendo | 1 |
| Hive Queen | circle | radius 400 | 7000 + 4 respawning anchors | from authored abilities | beacon_clearers | 1 boss + 4 anchors |
| Reactor Core | rectangle | 800 × 400 | 6999 (3 × 2333 valets) | from authored abilities | light_pressure | 1 untargetable carrier + 3 valets |
| Doomsayer | circle | radius 360 | 10000 | from authored abilities | storm | 1 |
Apply the tier × depth multiplier from the previous table to both the HP pool and the bar damage to get the mini-boss values for a given run slot.
Add-pressure profiles run alongside the boss
| Profile | Trigger | Add type | Count per wave | Spawn position |
|---|---|---|---|---|
| none | — | — | — | — |
| light_pressure | recurring every 8 s from t=4 s | orb (common) | 3 | arena edge, random |
| heavy_pressure | recurring every 12 s from t=2 s | gunner (common) | 5 | cardinal points |
| beacon_clearers | recurring every 15 s from t=10 s | charger (common) | 2 | opposite the player |
| storm | recurring every 20 s from t=15 s | gunner (common) | 8 | ring around the arena |
| crescendo | t=0 s, then HP phase crossings | gunner (common) | 2 / 4 / 6 | cardinal / ring / ring |
Sealed arena footprint
| Field | Value |
|---|---|
| Shape | square |
| Half-extent | 1400 world units |
| Side length | 2800 world units |
| Wall thickness | 2000 world units |
| Player spawn | arena center |
| Player invulnerability on entry | 3 seconds |
| Closing animation duration | 8 seconds (declared per boss; sealed arenas appear at full size instantly) |
| Biome world-gen inside arena | skipped |
| Biome events inside arena | suppressed |
| Background spawner inside arena | suppressed (only the boss roster and the add-pressure profile spawn) |
Rewards on mini-boss kill
| Boss | XP | Currency | Extra level-up reward picks | Cascade ring composition |
|---|---|---|---|---|
| Killer Croc | 500 | 50 | 1 | 2 × comet fragment, 1 × volatile crystal, 1 × magnetar pulse, 1 × scrap pile |
| Prism Cluster | 800 | 80 | 1 | 2 × scrap pile, 1 × mineral vein, 1 × comet fragment, 1 × magnetar pulse |
| Junkrat Captains | 700 | 70 | 1 | 2 × volatile crystal, 1 × comet fragment, 1 × magnetar pulse, 1 × scrap pile |
| Digbot Swarm | 1000 | 100 | 2 | 2 × scrap pile, 1 × mineral vein, 1 × comet fragment, 1 × magnetar pulse |
| Awakened Mech | 1200 | 120 | 2 | 2 × drone wreck, 1 × mineral vein, 1 × magnetar pulse, 1 × scrap pile |
| Hive Queen | 900 | 90 | 1 | 3 × scrap pile, 1 × mineral vein, 1 × magnetar pulse |
| Reactor Core | 950 | 100 | 1 | 2 × comet fragment, 1 × mineral vein, 1 × magnetar pulse, 1 × scrap pile |
| Doomsayer | 1500 | 150 | 2 | 1 × scrap pile, 1 × mineral vein, 1 × comet fragment, 2 × magnetar pulse |
Mini-boss kills always fire one cascade ring at the death anchor. The reward composition is per-boss; the default fallback ring (used when a boss does not declare one) is 2 × scrap pile + 1 × mineral vein + 1 × comet fragment + 1 × magnetar pulse.
Reward chamber ring placement
| Field | Value |
|---|---|
| Anchor position | last-sharer-death position, falling back to a still-alive boss anchor, falling back to arena centre |
| Cascade rings spawned | 1 (mini), 2 (final boss) |
| Ring jitter on a second ring | up to ~80 world units in x and y |
Per-mini-boss-kill effects in addition to the cascade
| Effect | Trigger |
|---|---|
boss_kill signal fires with the boss’s XP, currency, and def id | encounter end on the win path |
| Per-prop break synergies | each cascaded prop rolls its own break-synergy effect |
| Sealed arena teardown | walls drop, terrain pattern is culled |
| Level advance | game._bossLevelCleared flag set; the engine progresses to the next level kind |
| Level-up reward picks granted | extraRewardPicks from the boss def, in addition to the level-up choice the level granted on its own |
How it works
A run is a fixed five-level (normal) or ten-level (challenge) sequence. Level kinds are resolved by index from the run-progression sequence; level 3 in both modes is always a mini-boss level.
When the engine advances into a mini-boss level it tears down any prior arena, skips biome world-gen, spawns a sealed square room of side length 2800 around the ship, suppresses the background spawner, picks a random boss def from the mini pool (or uses the override id on the run node), and calls the boss-spawn entry point with the mini tier flag. The roster is materialised from the def using the boss’s arena spec, the arena terrain pattern is applied, persistent boss VFX layers are registered, and the add-pressure profile is armed.
The mini tier flag multiplies the authored HP and damage of every body in the roster by the mini-tier HP and damage multipliers. The engine then multiplies both numbers again by the depth ramp, which scales linearly with the level’s position inside the run. The same boss def used at the final-boss slot of the same run will spawn with twice the HP and twice the damage of the mini-boss version, before depth scaling.
The level ends when the roster’s shared health pool reaches zero. The win path fires the boss_kill signal carrying the def’s XP, currency, and id; spawns the reward chamber cascade at the death anchor; sets game._bossLevelCleared; and the level controller advances to the next level. The player keeps any level-up reward picks granted by the boss def. The player’s level-up choices keep functioning normally throughout the encounter.
The AI Director continues to run during a mini-boss encounter and continues to feed its heat-driven personality, fire-rate, and aggro-range modifiers into every alive enemy, including the roster bodies and the add-pressure profile’s adds.
Interactions
The mini-boss pool and the final-boss pool draw from the same boss def registry, with the kind tag selecting which slot each def is eligible for. Every shipped boss is currently in the mini pool, and the final-boss slot picks from the same set with the boss-tier multiplier applied. A boss that ships at kind “boss” later will become final-boss-only.
The depth ramp applies to every boss-level spawn equally, so the same mini-boss def is harder at the third mini-boss slot of challenge mode than at the first. In challenge mode the second and third mini-boss slots are stronger than the normal-mode mini-boss slot.
The add-pressure profile attached to the boss def is the only source of non-roster enemies during a mini-boss encounter. Biome-pool spawning, biome events, hub/spoke loot props, and ambient lanterns are all suppressed inside the sealed arena.
The reward chamber cascade composition is authored per boss def. Each cascaded prop rolls its own break-synergy effect when broken, so clearing the ring after a mini-boss can chain several pickups in one beat.
Challenge mode payouts are doubled at run-assembly time. The XP, currency, and reward-pick numbers in the table above are the authored per-def values; the run wrapper around them applies the challenge-mode payout multiplier where applicable.
What it does NOT do
It does not introduce mini-boss-only enemies. The mini-boss is always one of the boss-pool encounters, run at the mini stat tier; there is no elite-enemy variant pool that only appears in mini-boss slots.
It does not extend or shrink the run length. Mini-boss slots are fixed at level 3 (normal) and at levels 3, 6, 9 (challenge); they cannot be re-rolled out of the sequence.
It does not impose a time limit. There is no timer on a mini-boss level, no soft timer, no escape mechanic. The only outcomes are killing the roster or dying.
It does not generate biome terrain inside the arena. The arena is a self-contained square; biome hubs, spokes, events, lanterns, and loot props do not appear.
It does not let the background spawner run. Only the boss roster and the add-pressure profile attached to the boss def can spawn enemies during the encounter.
It does not drop the run-end portal. A mini-boss kill advances to the next level directly; the portal walk-through exists only on the legacy out-of-sequence path used by dev and playground scenarios.
It does not scale rewards with depth. XP, currency, extra reward picks, and the cascade ring composition are authored per boss def; the depth ramp tightens the fight but does not change the payout.
It does not preserve boss-fired projectiles after a player death. Roster bullets persist for their natural lifetime on player death and are cleared instantly on win or level exit.