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