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