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