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