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