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