World Tier III in Diablo 4 is called Nightmare mode and with it comes increasingly difficult monsters, new dungeon mechanics and plenty of lucrative loot that you'll want to get your hands on.
Nightmare Mode is only available once you have completed the campaign. It is recommended for Levels 50+, but you can join the World Tier III at any level as long as you have completed the required quests.
There are a total of four World Tiers available in Diablo 4.
Once you complete the Campaign, you'll have a brand new quest added to your Quest Log that will allow you to unlock Nightmare Tier.
Cathedral Of Light - Capstone Dungeon - Veteran
In order to unlock Nightmare mode you need to complete the Cathedral Of Light - Capstone Dungeon in Veteran mode (World Tier II).
You can find the Cathedral Of Light at Kyovashad and it is recommended you be around Level 50 for this dungeon.
Check out the video below for a full guide of the Dungeon:
Collect Animus from the Revenant Knights
The first task in this dungeon is to collect Animus, which drops from Revenant Knight Elite Mobs. You'll see a progress bar on the right hand of the screen showing you how much more you need to collect.
You'll find around 5 Revenant Knights in this part of the Dungeon. They come with several Elite Affix Types that can cause you issue:
- Summoner - Spawns extra mobs
- Lightning Enhanced - Uses electric attacks
- Teleporter - Can teleport away and on top of you with lightning attacks
You'll also find the following mobs:
- Knight Errant
- Knight Penitent (Elite)
Once you have enough Animus, head to the Animus Orn and deposit your Animus into it to open the gates to the next part of the dungeon.
In this part, you'll need to locate the High Council Court. A few new Skeleton mobs can be found here, but nothing signifcant to worry about.
High Council - Boss Fight
The first boss fight of the Cathedral Of Light dungeon is the High Council.
This fight composes of four different bosses that you have to take on all at once:
- Sacred Physician
- Grand Inquisitor
- Lord Commander
- Devoted Champion
The Sacred Physician should be your main target first. This boss can revive the other three, so try to take this one out first.
Then you should focus on Grand Inquisitor and Devoted Champion, and finally seeing off the Lord Commander.
When you defeat the Lord Commander, a round of mobs will rush towards you so make sure you have some AOE available.
Once defeated, head to the Teleporter at the top of the room to go to the next part of the Dungeon.
Reliquary Of Erudition
The next part of the dungeon requires you to slay all monsters in the Reliquary Of Erudition.
The mobs you can find here are:
- Knight Errant
- Knight Penitent (Elite)
- Inquisitor (Elite)
- Skeleton Archer
- Skeleton Corpse Bow
- Skeleton Corpse Axe
- Skeleton Captain (Elite)
- Crokhar Thunderdancer (Elite)
Once you defeat them all, it's time for the final boss fight. Head to the Curator's Chamber to begin...
The Curator - Boss Fight
Since this boss has a ton of health, you'll want to work on getting it's Stagger Bar up.
This stagger bar can be seen under it's HP bar and certain skills will increase it (usually your Cooldown attack skills). Once the Stagger bar is up, the boss will be stunned for several seconds and become very weak, allowing you to deal a mass amount of damage.
The Curator has several attacks to watch out for in the beginning. He'll shoot out three wisp attacks that can be dodged by darting forward. And he'll also shoot out a green pulse attack that is highlighted on the floor.
One of his main attacks to watch out for is the teleporting green pulse attack; in quick succession The Curator will teleport all around the map and blast out several green pulses, making them very hard to dodge.
He will occaisionally summon mobs so save any powerful AOE skills for when this happens. He also summons slow moving whirlwinds that can get in your way and make you vulnerable.
Good luck with this fight!
Once defeated, you'll have officially unlocked World Tier III - Nightmare mode! You can change the mode from the World Tier Statue in Kyovashad or at the character select screen.