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 statue of the fox.
Find the ancient battlefield.
Find the dwellings of the rift cult.
Speak to all of the spirit animals.
Completed the game.
Find the Ancient Llamba.
Complete the Monastery.
Discover all areas of the map.
Find Erin when she's gone.
Find the bones of an old beast.
Find the giant birdshrine.
Complete the Archives.
Find the chiseled stone map.
Find the statue of crane.
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.