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