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