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