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