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