Here is the full list of all 12 FEZ achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Find ALL collectibles.
Collect all 32 Golden Cubes and 32 Anti-Cubes.
Find the Skull artifact.
Reactivate all 5 warp gates.
Find the Tome artifact.
Get to the end.
Find the Writing Cube artifact.
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Find the Counting Cube artifact.
Find an Anti-Cube.
Break the code.
Find your very first cube shard.