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