6-man Godslayer Mode Triggers

Kang Pagoda - Don't pull the adds down stairs. Fight them with the boss.

Reliquary of Flame - Kill the Abbot add, loot the oil from him, place it on the fire before the boss spawns.

Vortex of the Storm - Talk to either the air or water adept before the fight.

 Originally Posted by MagnusLL 

A little tidbit that I vaguely remember and that no one ever mentions: in vortex of the storm, whether you talk to the air or to the water adept to trigger hardmode changes the resulting fight.

If you talk to the air adept, you get more tornadoes. If you talk to the water one, water rises more quickly.

Coppice of the Heart - When entering the boss' room, only break the outer membrane.

Final Boss (Kahn) in Pillars of Heaven - Stop attacking him when he kneels down at 25% health.

Jade Dugout - Don't kill anything in boss room before bossfight starts. Tank must talk to slaves without pulling any soldier. 

Den of Crowmen - Get the egg to 50% and stop attacking it until a 2nd boss pops from it.

Abyss of Kun Whu - Do not kill the healers that spawn at 50%.

Palace of Yun Rau - DPS boss to 90% health while the healer is still alive.

Cavern of Malice - You need to burn the Demon down to 10% or less so it triggers his line. Then let him get the children to under 10% and it will trigger a line from them, you then have to quickly kill the Demon.

Celestial Necropolis - Once the first pillar is activated, and the spirit guardian is killed. Stand on the plate and emote /curse, before you do the correct emote.

Enigmata of Yag - Once the boss inside is at ten percent, destroy the outside recepticle.


Ai District - Kill Commander Yah-Weng(?) and stick his head on the spike that overlooks the final boss area.

Tian'an District - Kill all 4 bosses (ironwright, rhino, shadowmaster, drunkard) before Armsmaster sets fire to their part of the map.

Ardashir Fort - Kill all the small crabs before starting Sodabeh.

Iron Tower, Desumo - At 75%, everyone must get on correct squares very quickly (3 seconds?) WITHOUT stepping on any square they don't have gem for.

Iron Tower, Guardian - Keep all golems away from others, if any of them merges hardmode fails.

Xibaluku - From the moment first player enters instance; kill Surberec (dog) in 8 minutes to get Relic of Iziel Al'zeep (check your bags), then use the relic on Altar of Dark Sorcery under Tia Shar's room before the timer on it expires. Holder of relic must not die.

Vile Nativity, Argo Satha - Use the scroll from ghost statue room (curse of the lich?) on him.

Vile Nativity, Little Prince - Don't kill the nursemaids.


rogue

tainted weapons - heal remover

Abyss of Kun Whu (HM) - green icon at 50%, heal can be removed through shield
Cavern of Malice (normal and HM) - removing heal from one girl (blue icon)
Celestial Necropolis (normal and HM) - removing heal bubble after joyous adds
Coppice of the Heart (HM) - removing the 3 PPM heal from boss (green icon)
Enigmata of Yag (HM) - kraken boss (Spawn of Nyarlathotep), Leviathus boss (X'cth the Annihilator)
Yun Rau (HM) - removing heal from boss (green icon)
Vile Nativity - Idols of Silence encounter, removing Light of Atlantis heal on one of the statues

finely honed - bubble and damage reflection shield remover (doesn´t need a perk slot)

Cavern of Malice (HM) - removing the bubble at 75%, 50%, 25% when sisters come together
Enigmata of Yag (HM) - kraken boss (Spawn of Nyarlathotep), Leviathus boss (X'cth the Annihilator)
Reliquary of Flame (HM) - removing of "Burn Skin" bubble; 2nd can´t be done within CD, those first seconds can be overcome by necro/BS protection buff
Yun Rau (HM) - removing the reflection shield (Jhebal Blessing-like effect) from boss before starting the tanking, otherwise returns cca 500dmg/hit
Vile Nativity - Idols of Silence encounter, removing Molten Shield bubble on one of the statues


soldier

resolve - wrack remover (only from the soldier himself)

Cavern of Malice (HM) - removes debuff received from Mei-Lin that decreases damage done by tank by 50%
Den of the Crowmen (HM) - removes wrack received from small bird decreasing damage mitigation by 10%/stack
Enigmata of Yag (HM) - worms "Parasitic Spray" + every HM boss
Pillars of Heaven (HM) - removes debuff received from the true boss form decreasing incoming heal by 10%/stack 
Ardashir Fort - removes wrack from tank hit by the rhinoboss charge, removes snaring wrack (black-red icon, Wrackling Stab spell) casted by crabs and removes wrack casted by Sodabeh on 2nd phase of the HM encounter


priest

steadfast faith - all ruin and some torment remover: 
torment: BS - physical, ToS - elemental, PoM - spiritual

Abyss of Kun Whu (HM) - stacking debuff on tank dealing percentual unholy damage
Celestial Necropolis (normal and HM) - "Mind Ruin" (elemental icon) decreasing damage received from grieving add
+ PoM - exploding "Ghostly Torment" (spiritual icon) received from conceeding add
Den of the Crowmen (HM) - debuff received from big bird decreasing incoming heals by 50%
Enigmata of Yag (HM) - worm and Chatha boss (Tetharos the Slaughterer), kraken boss (Spawn of Nyarlathotep)
Yun Rau (HM) - oneshot spell "Netherfrost" received from boss on random group member, in case of emergency can be canceled by the fire pulses from bowls
Ardashir Fort - removes ruin from player hit by the rhinoboss charge, removes ruin (red-black icon) from players casted by Sodabeh on 2nd phase of the HM encounter


mage

unbinding charm - (all) torments remover

Celestial Necropolis (normal and HM) - exploding "Ghostly Torment" (spiritual icon) received from conceeding add
Coppice of the Heart (normal and HM) - works like root remover on "Deadweight" spell
Abyss of Kun Whu - removes charm effect from another player



other

elusive nature - provides % to critigation chance, that means chance to decrease critical hit by critigation amount from Khitai armor a AA (Forced Engage - soldier perk)
- General perk, for all classes, in PvE mostly needed for tanks

Den of the Crowmen (HM) - both birds 
AI District - Commander

Add this stuff to first post:
Ai District: Kill Commander Yah-Weng(?) and stick his head on the spike that overlooks the final boss area.

Tian'an District: Kill all 4 bosses (ironwright, rhino, shadowmaster, drunkard) before Armsmaster sets fire to their part of the map.

Ardashir Fort: Kill all the small crabs before starting Sodabeh.

Iron Tower, Desumo: At 75%, everyone must get on correct squares very quickly (3 seconds?) WITHOUT stepping on any square they don't have gem for.
(for the record: this is the stupidest trigger ever)

Iron Tower, Guardian: Keep all golems away from others, if any of them merges hardmode fails.

Xibaluku: From the moment first player enters instance; kill Surberec (dog) in 8 minutes to get Relic of Iziel Al'zeep (check your bags), then use the relic on Altar of Dark Sorcery under Tia Shar's room before the timer on it expires. Holder of relic must not die.

Vile Nativity, Argo Satha: Use the scroll from ghost statue room (curse of the lich?) on him.

Vile Nativity, Little Prince: Don't kill the nursemaids.

Sepulcher of the Wyrm: Is there a hardmode?