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