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