Here is the full list of all 8 Defy Gravity Extended achievements. It takes around 4-5 hours to unlock all of the achievements on Windows.
Prove yourself as a Grand Master Gravitymancer
Prove yourself as the Gravitymancer Emperor
Prepare yourself for the real Gauntlet
Transcend all Gravitymancers and become The One
Enter the Gauntlet
Prove yourself as an Apprentice Gravitymancer
Prove yourself as a Gravitymancer Warrior
Prove yourself as a Master Gravitymancer