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