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