The The Fate of Atlantis - Episode 3: Judgment of Atlantis Add-on for Assassin's Creed Odyssey has 5 achievements worth 130 gamerscore.
Kill 10 Isu Soldiers with the Blessing of Kronos enhancement.
Completely fill the Knowledge Sequence.
Forge the 3 Legendary Weapons.
Collect all the Keeper's Insights in Episode 3.
Defeat the Hekatonchires.