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