Released in Final Fantasy XIV with patch 6.1 of Endwalker, players can get into this Alliance raid and fight as a 24 people group.
Once you have unlocked two Alliance Raids they'll be available in the daily Alliance Raid Roulette along with any other Alliance Raid you might unlock later.
Unlocking The Myths of the Realm Part 1: Aglaia in Final Fantasy 14
In order to unlock the Alliance Raid, you will first need to complete the new Chronicle of a New Era quest called "A Mission in Mor Dhona" introduced in patch 6.1.
This quest can be taken from the Fresh-faced Student in Old Sharlayan (X:9.1 Y:11.5) after having progressed enough in the 6.1 story quests.
Once that's done player will be able to unlock the Alliance raid via the new quest available there.
Everything about FFXIV Endwalker
Endwalker is the new expansion for Final Fantasy XIV, released on December 3rd. We'll do our best to cover all the new stuff and produce any guides you may need during the expansion, you can also take advantage of our many guides on content already available here.