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