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