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