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