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.
Step into the well.
Find the ancient battlefield.
Find the Ancient Llamba.
Find the statue of the fox.
Find the statue of the deer.
Get some Lambaby love.
Completed the game.
Complete the Archives.
Find the giant birdshrine.
Find the chiseled stone map.
Find the statue of crane.
Discover all areas of the map.
Speak to all of the spirit animals.
Find Erin when she's gone.
Find the bones of an old beast.
Complete the Monastery.
Find the dwellings of the rift cult.
Complete the Eventide Sanctuary.
Find the Crab Island.
Escape the collapsing cave.