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