Overview
Path of Exile 2 has 7 farmable Endgame Mechanics:
- Delirium
- Citadels + Arbiter
- Trial of Sekhema
- Trial of Chaos
- Ritual
- Expedition
- Breach
The second of the 7 Mechanics are the Citadels and the Arbiter, the main 'Storyline' and Pinnacle Boss of the Endgame.
Citadels

On the players' journey through the Endgame, they might find beacons of light in the fog. Once getting closer they will discover that the origin of the beacons are Citadels, the Endgame contains 3 different Citadels. One for each of the 3 Acts of the Campaign. The 'Guardian', the boss of the respective Act waiting at the end of it. Each Citadel has a special set of Maps that can only spawn around it. Selected from the Tilesets of their acts and manned with bosses specific to their act.
Iron Citadel

White/Grey Beacon, Act 1 Endboss
Copper Citadel

Orange Beacon, Act 2 Endboss
Stone Citadel

Red Beacon, Act 3 Endboss
Fragment Drop Calculation
Currently, we do not know the exact numbers where additional Fragments drop. Based on the data so far the following is assumed:
- 0%-200% - Chance for 1 additional Fragment
- 200%-900% - At least 1 additional Fragment, Chance for 2
- 900%+ - At least 2 additional Fragments, Chance for 3
Arbiter of Ash

Once a player has collected or purchased all 3 Fragments they can challenge the Endboss the Arbiter of Ash, with the recent 0.1.1 Patch the player has 6 Attempts, reducing down by one for each increase in Difficulty.
How to farm Citadels
The best way to farm Citadels is to allocate the Delirium Node 'Get out of my Head!' and run/sustain any % Delirious Maps, passively generating Simulacrum Splinters while rushing through the Maps looking for Citadel Beacons. Keep the most stacked Maps with as much Keystone Drop chance as possible for the Citadels. It is also recommended to allocate the Atlas Keystone 'Unstable Energies', the 25% more Effect on Suffixes will increase the Waystone Drop chance further.

It is further recommended that the Fragments be sold for a stable profit. Attempting the Arbiter is only recommended in larger quantities to improve the odds of hitting a well rolled Unique
How to farm Arbiter
Either go for the above and self-farm your Fragments or buy the Fragments over the Currency Exchange.
The Arbiter's loot value is weighted against the value of the fragments. So, a profit is usually guaranteed if several runs are made, while a single run might yield some profit or lose some.
The most valuable drop from the Arbiter are specific rolls on the Prism of Belief or Morior Invictus. A good way to yield additional gains is to use the Arbiter Atlas Passive Tree Nodes
- Central Terraformer for Rare Precursor Tablets that can sell for a lot if rolled well or in bulk
- Witness to History to improve the odds of getting a high-Value Unique
- Lost Technique for a chance of a Level 20 Gem or Spirit Gem
