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