Boss Rush

Boss Rush Mode is an alternative game mode that is accessible in the starting area of the Prisoners' Quarters. In this mode the player can fight bosses back-to-back with items they receive throughout the trials, without traveling through the regular biomes. It has 4 trials, with only the first being unlocked at the start. Completing a trial will unlock the next one.

Access
To access the Boss Rush, one needs to encounter at least 3 bosses (one Tier 1, one Tier 2, and one Tier 3). Though accessing the 3rd & 4th trial that contain 5 bosses instead of 3, one needs to encounter at least 5 bosses (two Tier 1, two Tier 2, and one Tier 3). If the player has encountered additional bosses, then those can be randomly chosen as a Tier 1/2/3 boss during a trial.

Gameplay
At the start of a rush, there is a choice between Brutality, Tactics, and Survival in the form of three Stat-Stones. Choosing one will automatically give the player stats relevant to the chosen colour and supply the player with 3 choices of relevant builds at the start of the trial in the form of tubes. Once a colour is chosen, the play won't be able to change the colour, nor find items that don't scale with the main stat during the run (the only exception is the first colourless altar). Interacting with a second and third Stat-Stone will increase the stats of the player.

Each boss drops loot in the form of two items (one weapon and one skill) and a fixed amount of gold. The last boss will only drop around 150-300 cells (depending on the trial), which can be invested into the Legendary Forge.

These items are disabled during Boss Rush:
 * Spoiler Skill
 * Spoiler Skill

Transition Rooms
These will be present in every transition room:
 * Guillain: Players are able to choose mutations in every transition room during a trial.
 * The first reroll will always be free.
 * Though rerolling mutations further will cost gold.
 * Rerolling will never cost money in the first Guillain.

These will be present in every larger transition room (after every boss in the 1st & 2nd trial and after every two bosses in the 3rd & 4th trial):
 * Stat-Stone: Interacting with it gives the player more stats.
 * Item-Altar: A two-choice-altar (with a weapon and a skill) will appear at the beginning of the transition area.
 * A colourless three-choice-altar (with one guaranteed weapon & skill) will appear at the beginning of a run, but it can only provide items of the chosen colour.
 * If the previous boss has been slain flawlessly, then a legendary three-choice-altar (with one guaranteed weapon & skill) will appear instead.
 * This only happens in Trials 2 & 4.
 * Blacksmith: Players are able to upgrade items or reroll their affixes.
 * Shops: Two shops (weapon & skill) will provide the player with more gear.

At the end of a run:
 * Legendary Forge: After the run has been completed, the player gets the choice to invest their Cells into the Legendary Forge.
 * Loot: A chest that contains rewards is located at the end of the last transition area, alongside the Mentor Knight NPC.

Items
Rewards are locked behind specific conditions:
 * (Trial 1)
 * (Trial 2)
 * (Trial 3)


 * (Trial 4, 0-2 BSC)
 * (Trial 2, 3-4 BSC)
 * (Trial 3, 3-4 BSC)
 * (Trial 4, 3-4 BSC)
 * (Trial 2, 5 BSC)
 * (Trial 2, 5 BSC, flawless)
 * (Trial 3, 5 BSC, flawless)
 * (Trial 4, 5 BSC, flawless)

The Statue
A statue of the Beheaded, which has customizable parts. The statue itself is unlocked by beating the 1st trial. New parts are locked behind Boss Rush victories. To unlock every statue reward, the player needs to clear every trial at least 6 times:
 * 0-2 BSC
 * 3-4 BSC
 * 5 BSC
 * 0-2 BSC, flawless
 * 3-4 BSC, flawless
 * 5 BSC, flawless





Trials
There are 4 different trials in Boss Rush, with each being harder than the previous. A 3 bosses and 5 bosses trial, without and with modifiers. The player will be fighting alternative versions of bosses with extra abilities in the trials with modifiers.
 * Trial 1:
 * 3 bosses back-to-back
 * One Tier 1, Tier 2 & Tier 3 boss
 * Trial 2:
 * 3 bosses back-to-back with modifiers
 * One Tier 1, Tier 2 & Tier 3 boss
 * Trial 3:
 * 5 bosses back-to-back
 * Two Tier 1, two Tier 2 & one Tier 3 boss
 * Trial 4:
 * 5 bosses back-to-back with modifiers
 * Two Tier 1, two Tier 2 & one Tier 3 boss

Bosses will be selected from these 3 tiers:
 * Tier 1:
 * The Concierge
 * Conjunctivius
 * Mama Tick
 * Tier 2:
 * The Time Keeper
 * The Giant
 * The Scarecrow
 * Tier 3:
 * The Hand of the King
 * The Servants (final fight)
 * The Queen

The Concierge

 * Twins: A second Concierge is in the fight.
 * They don't scream or create a force shield upon changing phases.
 * They only have 4 phases
 * They don't gain attack speed on low HP (stage 5 & 6 mechanics).

Conjunctivius

 * Conjunctivius only moves once instead of twice between attacks.
 * Spawns up to 4 Tentacles continuously. (Needs verification)
 * She only has one Tentacle Phase:
 * Activates when she reaches 50% HP.
 * Will spawn 5 additional Tentacles.
 * If one didn't slay the continuously spawning Tentacles, then there can be up to 10(?) Tentacles.
 * She screams a total of 5 times:
 * 1st scream at 90% HP (Bullet Hell afterwards)
 * 2nd scream at 70% HP
 * 3rd scream at 50% HP (Tentacles afterwards)
 * 4th scream at 30% HP (Bullet Hell afterwards)
 * 5th scream at 10% HP

Mama Tick

 * New attack: Unique Scythe Stabs that move from:
 * Left to right
 * Right to left
 * Middle to edges
 * Edges to the middle

Time Keeper

 * Heals to full health after transitioning to her 3rd phase.
 * She skips her first phase on 1BC+.
 * General cooldown reduction on attacks and between attacks.

The Giant

 * Has 4 hands instead of 2
 * Attacks with two hands in quick succession (double swipe, double slam, slam-swipe, etc.).
 * Starts in phase 3. (Needs confirmation)

The Scarecrow

 * Stomp:
 * Throws 4 Sickles instead of 2 per Stomp.
 * Seed Throw:
 * Throws 2 Sickles per Seed Throw.
 * Can now spawn up to 4 mushrooms instead of only 3.
 * Pitchfork Jab:
 * Can spawn a Yeeter with the first attack.

The Hand of the King

 * Has a different AI that forces more moves (Slash-Slam into Super Slam, 4 Charges, etc.).
 * Is also more aggressive.
 * Has a new two-combo attack:
 * The first Slash's hitbox extends behind HotK and has the sound cue of the Time Keeper's Hook Throw.
 * The second Slash is similar to the third Slash in his Triple-Slash attack.
 * Added a 2nd slam after Slash-Slam.
 * Doesn't use his Exploding Flags attack.
 * Starts in Phase 3, but has an enemy phase.
 * Spawns HPC enemies during phase change.

The Servants

 * Arena now has wall Spike & Ball Spike traps on the walls and ceiling.
 * They are more aggressive.
 * All three servants can be in the arena at the same time.
 * Euterpe:
 * She can use her normal attack up to 5 instead of 3 times.
 * Her Arrow Salve will fire 15 (3x5) instead of 9 (3x3) arrows.
 * Her Stomp's AoE will hit a second time after a brief moment.
 * And more changes for all three Servants. Their attack patterns also change depending on the number of Servants alive,

The Queen

 * Normal attacks cause Reality Slashes with different angles:
 * Slash: Upwards angle
 * Stab: Horizontal
 * Lower-Stab: Downwards angle
 * Special attacks cause Reality Slashes with different angles:
 * Down-Strike: Vertical
 * Dashing-Strike: Horizontal
 * Her Melee Parry causes another horizontal Reality Slash.
 * Is invulnerable during her Reality Slashes.
 * Her 2nd Reality Slashes phase is faster.

Gold
The gold values are vastly different in Boss Rush:
 * Bosses drop 2500 gold.
 * Selling:
 * Items (including flasks) can be sold for 260 gold.
 * Blacksmith:
 * Rerolling affixes costs 200 gold.
 * Upgrading an item costs 800 gold.
 * Shops:
 * Items cost 1750 gold.
 * 1st reroll: 1950 gold.
 * 2nd reroll: 2100 gold.
 * 3rd reroll: 2300 gold.
 * 4th reroll: 2450 gold.
 * Guillain (mutations):
 * 1st reroll: free.
 * 2nd reroll: 2000 gold.
 * 3rd reroll: 4000 gold.
 * 4th reroll: 8000 gold.
 * The cost caps at 8000 gold, but resets with each new Guillain.

Gear & Stats
The gear level of items from Boss Rush will be affected by the difficulty bonus (+1 level on 3BC and +3 levels on 4-5BC).

This is a table for all the gear levels:

This is a table for the number of stats one has after interacting with the Stat-Stones: