Here is the full list of all 24 N.E.R.O.: Nothing Ever Remains Obscure achievements worth 1,000 gamerscore.
Find the plate of gnocchi on Thursdays.
Complete the Staircase Entrance Puzzle.
Complete the last puzzle leading to the end.
Complete the Falling Tree puzzle.
Solve all the puzzles within the game.
Successfully solve all SOLARIS puzzles in the game.
Find all of the mementos in the hospital.
Find all the mementos in the game.
Find all of the mementos in the desert.
Complete the NERO experience.
Find six mementos in the desert.
Complete the hospital.
Find six mementos in the hospital.
Complete the forest.
Find all of the mementos in the forest.
Find six mementos in the forest.
Complete the crystal caves.
Find all of the mementos in the crystal caves.
Awarded after the reunion.
Complete the Three Wise Monkeys Puzzle.
Find six mementos in the crystal caves.
Complete the first Sphere of Light puzzle.
Solve the first puzzle and enter the caves.
Find a memento.