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