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