Originally posted by Glubbable:

Bosses are also broken down into specific boss packs, in order to provide a more randomized rotation of bosses and to understand what combos of bosses could occure for specific packs during a special around, like double trouble. This also helps decrease the load & download times for the server & client.

Intro:
• None

When it's close:
• Static buzzing and electrical sounds including blaring and crackling.
  
• Interface starts shaking.

Tips:
• Get out of his line of sight ASAP, you can achieve this through either hiding behind objects or using corners.

Origin:
• Somthing Awful.

Type:
• Tag Team Tier (Bosses that appear together and usually work together)
  
• Paranormal Tier (Bosses that use static and kill abilities along with teleportation.)
  
• Instakill
  
• Survivor Sandwich

Stunnable?
• No

Partners:
• Kate

Max Copies:
2

Jumpscare

Main Maps:
• Forgotten Tomb
• Claustrophobia
• Elementary
• Forgotten Tomb
• Hospice
• Sanatorium
• The Abyss

Intro:
• None

When it's close:
• Initial blaring, like with Slenderman.
  
• Interface starts shaking.

Tips:
• Get out of his line of sight ASAP, you can achieve this through either hiding behind objects or using corners.
  
• His relatively easier to escape from then his alter ego.

Origin:
• Christmas + Slenderman.

Type:
• Tag Team Tier (Bosses that appear together and usually work together)
  
• Paranormal Tier (Bosses that use static and kill abilities along with teleportation.)
  
• Instakill
  
• Survivor Sandwich

Stunnable?
• No

Partners:
• Kate

Max Copies:
2

Jumpscare
• Identical to Slenderman's jumpscare.

Main Maps:
• Forgotten Tomb
• Claustrophobia
• Elementary
• Forgotten Tomb
• Hospice
• Sanatorium
• The Abyss

Intro:
• None

When she's close:
• You hear coughing, gasps, hissing and whispers accompanied by static.

Tips:
• Use the mighty power of the flashlight to stun her.
  
• If she's nearby, her master is probably close too.

Origin:
• Slender: The Arrival (It's a good game.)

Type:
• Tag Team Tier. (Bosses that appear together and usually work together.)
  
• Paranormal Tier (Bosses that use static and kill abilities along with teleportation.)
  
• Instakill.
  
• Survivor Sandwich.

Stunnable?
• Yes

Partners:
• Slenderman
  
• Slendyclaws (Alternate outfit)

Max Copies:
2

Jumpscare

Main Maps:
• Forgotten Tomb
• Claustrophobia
• Elementary
• Forgotten Tomb
• Hospice
• Sanatorium
• The Abyss

Intro:
• None

When it's close:
• Groaning, grunting and related noises;
  
• Spotting you it will start making angryer noises (Like snarls).

Tips:
• Each swipe will send you flying, try use that as a boosted headstart to get away.
  
• Hitting it hard enough will stun it, as well as the good ol' flashlight. I don't reccomend trying to hit it with the flashlight itself though...

Origin:
• CreepyPasta

Type:
• Chaser Tier (Bosses that chase you relentlessly until exhaustion.)
  
• 65 Damage per hit.
  
• Annoyingly persistant.

Stunnable?
• Yes

Max Copies:
3

Alternate Skin
• Red-Nosed Rake

Main Map:
• Frost Run
  
• Classic Frost Run

Intro:
• Monoculus teleporting through the void SFX

When it's close:
• Ghostly groaning and moaning.

Tips:
• Pray for Mercy
  
• Use your Sprint wisely.
  
• They dissapear after a few seconds with no one to chase.

Origin:
• 2013 Scream Fortress event

Type:
• Mob Tier (Bosses that spawn in groups on a lone or grouped target.)
  
• Instakill
  
• Annoyingly persistant.
  
• Supreme Survivor Sandwich.

• Stunnable?
  
• No

Max Copies:
4

Jumpscare:
BOO!

Main Map:
• Lobby
  
• Classic No Exit

Intro:
• None

When she's close:
• You'll hear whispers and sudden noises.
  
• You'll hear a sharp fizzing sound with the first jumpscare.
  
• The second jumpscare is accompanied by a screech.

Tips:
• Keep your eye on them at ALL times but don't stare for too long or you'll die.
  
• Group = Good.

Origin:
• OC

Type:
• Statue Tier (Bosses rendered immobile while being observed.)
  
• Instakill

Stunnable?
• No

Max Copies:
3

On the left is when she teleports nearby. On the right is on death.

Main Map:
• SCP-087-B
  
• Classic 8 Pages
  
• Classic No Exit

Intro:
• WHAT ARE YOU DOIN' IN MA SWAMP?!?!

• When he's close:
  
• "Where is everybody?"
  
• Him roaring or going "Gaoohh" means he's found you.

Tips:
• His footfall is heard across the map when chasing.
  
• Keep vigilant.
  
• Don't run in straight lines.
  
• Looking at him will drain your sanity and eventually kill you.

Origin:
• Shrek

Type:
• Chaser Teir (Bosses that will chase you relentlessly until exhaustion)
  
• Instakill
  
• Danger level: Off the charts: Fast, no glow given, no kill delay, extreme persistance.

Stunnable?
• No

Jumpscare
• Donkey! *SMASH*

Main Map:
• Swamp

Intro:
• None

When it's close:
• Roars and grunts.
  
• As he runs, the ground shakes.

b]Tips:[/b]
• Easy to outrun

Origin:
• Left 4 Dead Series

Type:
• Tag team Tier (Bosses that appear and often work together)
  
• 120 Damage
  
• Easy to give up

Stunnable?
• No

Partner
• Witch

Main Map:
• Parish

Intro:
• None

When it's close:
• Sobbing, crying and screaming.

Tips:
• Pray for Mercy
  
• Stay as out of sight and far away as possible.
  
• Don't spam voice commands

Origin:
• Left 4 Dead Series

Type:
• Tag team Tier (Bosses that appear and often work together)
  
• Chaser
  
• Instakill
  
• Breaking the Speed Limit

Stunnable?
• Yes

Main Map:
• Parish

Intro:
• None

When it's close:
• You'll know...

Tips:
• It is extremely hard to see without your flashlight, but you'll hear it.
  
• Look at Villar, while it's chasing you to make it despawn (Hopefully.)

Origin:
• Slender Fortress

Type:
• Shadow Tier (Bosses that heavily rely on teleporting directly behind you.)
  
• Instakill (Rarely two shots a Heavy)
  
• What is "The Sound Barrier?" Don't count on outrunning it

Stunnable?
• No

Main Maps:
• Monophobia (Reborn)

Intro:
• "The Angels are coming for you, but listen. Your life could depend on this; Don't blink, blink and you're dead. They are fast, faster than you can believe. Don't turn your back, Don't look away and don't blink... Good Luck."

When it's close:
• Stone scraping.
  
• Tense chord.

Tips:
• Stare at them as you head for the stairs, but remember... Don't blink.
  
• Look hard in the darker areas for they are camouflaged.

Origin:
• Doctor Who

Type:
• Statue Tier (Rendered immobile when observed.)
  
• Instakill

Stunnable?
• No

Jumpscare:
• Neck snapping SFX

Main Map:
• Weepers
  
• Classic 8 Pages
  
• Classic No Exit

Intro:
• None

When he's close:
• "Scheisse!"
  
• Gunfire

Tips:
• Position yourself wisely, make use of the in-map healthpoints and ammo.
  
• Has an insane attack speed.

Origin:
• Wolfenstien 3D

• Ranged Tier (Bosses that are capable of attacking you at long ranges.)
  
• Built like a Tank

Stunnable?
• Yes (Killable)

Main Map:
• Wolfenstein 3D EP309

• Slender Fortress #1 (Standard) - 188.165.207.20:27015
  
• Slender Fortress #2 (Random bosses) - 188.165.207.20:27016
  
• Smash Fortress #1 - 188.165.207.20:27017

• Slender Fortress #1 (Standard) - 74.91.123.26:27015
  
• Slender Fortress #2 (Survival/Specials) - 74.91.123.71:27015

• Slender Fortress #3 (Random bosses) - 74.91.114.52:27015
  
• Slender Fortress #4 (Survival/Specials) - 74.91.114.167:27015

None of this would be possible without the efforts of Glubbable~ ❥, Vincentor, Simply Delicious, The Gaben, Chillax, Benoist3012 and Kit'o Rifty and the other many people that worked countless hours on this mod and their maps, Thank you.