Ambassador Hellmaw

Abilities

Fear: AoE fear spell with a 40 yard target range

Corrosive Acid: A cone attack, deals 1094-1406 nature damage per 3 seconds and reduces armor by 3938-5062

Fight

Ambassador Hellmaw should begin to wander the room once you've slain the final Cabal Ritualist, this gives you the choice of engaging now or retreating to drink/eat up before the fight.

Due to this bosses cone effect ability, Corrosive Acid, you're going to want to have you tank holding him turned away from the party, otherwise this ability combined with an untimely fear can deal quite a bit of damage to your now unorganized party. The only class able to avoid the fear is the hunter with feign death, otherwise anyone resisting the fear may be subject to an immediate beat-down unless they happen to be the tank.

Also, make sure to keep the tank topped off during Corrosive Acid due to the armor reduction, as mentioned before if the boss doesn't slaughter a few party members he may just end up bashing your tank's head in should he resist/keep aggro during the fear. Other than that this boss is somewhat easy, just keep alert for fears and such.

Blackheart the Inciter

Abilities

Charge: Random target is charged for around 400-500 damage.

War Stomp: AoE knockback attack, deals around 1000-2000 damage and wipes aggro.

Incite Chaos: Mind controls all party members for 15 seconds, unresistable and unremovable, wipes aggro.

Fight

The only real bad part to this fight would be the Incite Chaos ability, it triggers seemingly randomly and can be quite the surprise to those unfamiliar with the ability. During this period Blackheart will use up any cooldowns avaliable so everyone should use those right after engaging the boss rather than later.

Besides Incite Chaos you're going to want your tank pulling him into a corner or against a wall, allowing him to taunt/re-take aggro immediately after a War Stomp and thus avoid the boss running rampant.

Grandmaster Vorpil

Abilities

AoE Shadow Bolts: Hits everyone in the area with shadowbolts dealing 800-1200 damage.

Teleport Party: Teleports the entire party to his location.

Rain of Fire: Deals around 1000-1100 each tick, always cast after using Teleport Party.

Fight

Vorpil is quite the easy fight really, all you'll have to do is destroy the voidwalkers emerging from three portals located to the north, east, and southwest of the boss. These voidwalkers will immediately head directly for the boss upon exiting the portal, if they arrive the boss is healed and the voidwalker erupts for around 2000 damage. These voidwalkers are however easily slain and non-elite.

The next and last trick to this fight is his Teleport Party/Rain of Fire combo, simply explained Vorpil will teleport the party and himself to the pedestal and proceed to cast rain of fire upon his location. When teleported everyone should leap off the pedestal and out of the Rain of Fire as fast as possible, this can and should prevent anything but the most minor damage from this ability.

Murmur

Abilities

Murmur's Touch: A fifteen second duration debuff attack that will cause the targeted party member to explode for 2000-3000 AoE nature damage afterwards. This also debuffs the Shockwave effect upon them silencing for five seconds.

Resonance: Once Murmur is aggroed if for any reason nobody is within melee range he will debuff the party increasing nature damage taken by 2000. For every five seconds after this the debuff is renewed and the party takes damage equal to the extra nature damage added, this stacks every five seconds so 2000,4000,6000 etc.

Sonic Boom: This will show an emote "Murmur draws energy from the air..." The attack is an AoE blast dealing 5000-8500 damage and debuffs those hit with nature damage inflicted every three seconds, and movement speed is reduced by 90%

Fight

Before starting the fight at all it should be known that Murmur has an extremely low aggro range and thus you can position yourself as needed without being too wary, still, aggroing before ready would be most likely fatal. Your ranged DPS should spread out around Murmur in such a manner that it allows for them to avoid damaging other players when hit with Murmur's touch.

One of the most important things is to react as soon as someone gets Murmur's touch, whenever anyone receives this debuff the ranged DPS should already be spread out but any melee dps will need to break away and avoid the other part members. Secondly is Sonic Boom, either you have everyone retreat or prepare to heal your tank through the extreme damage of the attack, either way you're going to endure some trouble.

Due to the 90% speed debuff you may suffer through Resonance if your tank can't get back into position fast enough, however if your tank dies your probably dead anyway. Generally I go for leaving the tank on the boss, with good healing and shielding he should stay up and it feels the safest.

Finally, if you lose any melee able to tank the boss you're practically fated to wipe, Resonance will wipe out anyone left standing unless the boss happens to possess around 2-4% life or so left at this point.