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