Intended to herald the Jailer's reign on Azeroth, the first Lich King, Ner'zhul, proved unworthy in his master's eyes. The last remnants of the fallen orc's twisted soul were encased in spiked shadowsteel, condemned to everlasting torment for his failure. All who cross his path will share in his suffering.
Hit Orbs with 
Suffering to remove the shield on them.
When Orbs are killed you can pick them up and throw them off the edge to stop them dealing damage to the raid.
Dodge the 
Grasp of Malice cones.
After 80% dodge the 
Spite circles.
Be in a position where you will not get knocked off the platform when 
Malevolence is dispelled or expires.
Transcendence is useful for negating knockbacks from Malevolence or getting to the edge quickly to drop off an Orb of Torment.
Tiger's Lust is useful for carrying Orbs of Torment as it will negate the slow applied.
You can cancel knockbacks with 
Glide.
Infernal Strike is useful for getting Orbs of Torment to the edge.
Blessing of Spellwarding can be used to negate the knockback from Malevolence if you are in a bad position or as a defensive for Suffering.
If you find yourself caught in the middle of a Grasp of Malice zone, 
Divine Shield can save you from being knocked off.
Heroic Leap and 
Charge are both useful to counter knockbacks from Malevolence dispels.
Skull Bash can be useful to counter knockbacks from Malevolence dispels.
Death's Advance is useful for negating knockbacks from Malevolence or the slow applied from Orb of Torment.
Wraith Walk is very useful for carrying Orb's of Torment.
Anti-Magic Zone is best used on a 
Shatter cast or Malevolence dispels.
This is a single-phase encounter where Ner'zhul's armor will shatter at 80%, 60% and 30%. The shattering armor will deal a moderate amount of raid-wide Shadow damage.
Suffering - This is the main tank mechanic of the fight. A beam will shoot from the boss towards the active tank, and this beam will hit everything in a straight line all the way to the edge of the room. If any Orb's of Torment are hit by this, their 
Eternal Torment will be removed. Damage taken by Suffering is increased by 500% for 30 seconds, so you will want to avoid getting hit by this multiple times in a row.
Throughout the encounter, Orb's of Torment will spawn, and they will be protected with Eternal Torment reducing the damage they receive by 99%.
Orb with Eternal Torment Shield:
Orb without Shield:
Torment - Each Orb of Torment will pulse with Torment dealing a low amount of Shadow damage to the entire raid periodically. This damage will stop from the Orb if it has been removed from the encounter.
Sorrowful Procession - Once an Orb has been defeated, you can interact with it and pick it up. Whilst you are holding the Orb, your movement speed will be reduced by 30% and will take a small amount of ticking Shadow damage. Once you reach the edge of the room with it, an extra action button will appear, allowing you to throw it off the edge.
Grasp of Malice - Cones will appear from the centre of the room, going towards the edge of the room. After a few seconds, they will trigger Grasp of Malice, and any players caught inside will be knocked back and take a large burst of Shadow damage.
Malevolence - Two players will be debuffed with this, and this can be removed. However, when this debuff is removed either by being dispelled or the timer expiring, it will deal a moderate burst of Shadow damage to the raid and knock everyone away from that player. Therefore, it is important to group up and dispel these on the edge of the room, so you land on the platform.
Important Note: The player with the debuff will be knocked towards their back. Therefore they should face their character to the edge of the room so they are knocked to the middle.
Note: The knockback range is not that big on Normal/Heroic, therefore just being in the middle circle is sufficient for staying on the platform.
[Heroic] 
Lingering Malevolence - After a player has had mal removed from either dispelling or the effect expiring. A pool of Lingering Malevolence will be left behind.
Aura of Spite - Every 3 seconds a small pulse of Shadow damage will be dealt to the raid.
Spite - After a piece of armor has been shattered from Ner'zhul (80%), missiles will launch periodically. Any players hit by these will take a moderate burst of Shadow damage and cannot attack or cast spells for 3 seconds.
When Spite begins make a clear call not to dispel anyone with Malevolence.
Swing Timer: 1.8s (Curse of Weakness 2.16s)
Transcendence is useful for negating knockbacks from Malevolence or getting to the edge quickly to drop off an Orb of Torment.
Tiger's Lust is useful for carrying Orbs of Torment as it will negate the slow applied.
You can cancel knockbacks with Glide.
Infernal Strike is useful for getting Orbs of Torment to the edge.
Blessing of Spellwarding can be used to negate the knockback from Malevolence if you are in a bad position or as a defensive for Suffering.
If you find yourself caught in the middle of a Grasp of Malice zone, Divine Shield can save you from being knocked off.
Heroic Leap and Charge are both useful to counter knockbacks from Malevolence dispels.
Skull Bash can be useful to counter knockbacks from Malevolence dispels.
Death's Advance is useful for negating knockbacks from Malevolence or the slow applied from Orb of Torment.
Wraith Walk is very useful for carrying Orb's of Torment.
Anti-Magic Zone is best used on a Shatter cast or Malevolence dispels.