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