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