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