The The Fate of Atlantis Add-on for Assassin's Creed Odyssey has 15 achievements.
Destroy all of the Marble Maiden Tributes.
Kill 10 Isu Soldiers with the Blessing of Kronos enhancement.
Defeat the Hekatonchires.
Forge the 3 Legendary Weapons.
Completely fill the Knowledge Sequence.
Collect all the Keeper's Insights in Episode 3.
Dethrone the king.
Defeat all of the Fallen.
Close all Tartaros Rifts.
Collect all the Keeper's Insights in Episode 2.
Defeat Cerberos.
Win the conquest of Elysium with freed humans from the 3 main regions.
Kill all Overseers in Elysium.
Remember who you are.
Collect all the Keeper's Insights in Episode 1.