The Wanderer's Palace requires 4 players. The Wanderer's Palace can be unlocked at level 47+ (although it can only be attempted at level 50), by talking to Allene in Vesper Bay, Western Thanalan.
Players are awarded with 100 Tomes of Philosophy and 30 Tomes of Mythology of for completing The Wanderer's Palace.

Ampador Keep also requires four players and can only be unlocked through two different quests, Ghosts of Amdapor and Twisted Beliefs. Ghosts of Amdapor can be unlocked at level 50, after completing the main storyline quests and The Aurum Vale, players can Nedrick Ironheart in Vesper Bay, Western Thanalan. Twisted Belief is unlocked at level 50, after completing the main storyline quests, rank up to Chief Sergeant in your Grand Company, then talk to your Grand Company commander.
Players are awarded with 100 Tomes of Philosophy and 30 Tomes of Mythology for completing Amdapor Keep. (This dungeon is required for A Relic Reborn).