Ancient Tablets in Assassin’s Creed Odyssey are needed to upgrade your ship, the Adrestia.
There are two ways to get Ancient Tablets:
- From Ruins: Loot Ruins, they are the only place where you find Ancient Tablets apart from Blacksmiths. They aren’t found anywhere else. Ruins are marked by a red icon on the map: . By default these show up as Questions Marks “?” but when you get close enough it will reveal these places on the map.
- From Blacksmiths: Uncover the whole map and then visit every blacksmith in the game and buy up all their Ancient Tablets. Not every blacksmith sells them. In fact, it’s relatively rare that they do. This is better for the endgame when you’ve uncovered all areas and can quickly fast travel from one blacksmith to the next.
There are a lot more Ancient Tablets than you need to fully upgrade the ship. You don’t have to loot every single Ruin in AC Odyssey to get all the upgrades.
For All Locations refer to this guide: Assassin’s Creed Odyssey All Ancient Tablet Locations (Map).