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