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