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