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