Here is the full list of all 20 AER - there are Memories of Old achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Completed the game.
Find the chiseled stone map.
Complete the Monastery.
Find the Ancient Llamba.
Discover all areas of the map.
Find the dwellings of the rift cult.
Find the statue of the fox.
Find the ancient battlefield.
Speak to all of the spirit animals.
Find the bones of an old beast.
Find Erin when she's gone.
Find the giant birdshrine.
Complete the Archives.
Find the statue of crane.
Find the Crab Island.
Find the statue of the deer.
Step into the well.
Complete the Eventide Sanctuary.
Get some Lambaby love.
Escape the collapsing cave.