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