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