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