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