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