Finish the game by beating the Gorgon.

Going into the mission, try and have the max amount of mana potions and AE potions. With the warrior this was pretty easy. Once you get to the Gorgon apply invincibility if you have it. Once it's applied start hacking away. Once you're invincibility's up either drink some mana and activate it again or drink some AE and go into AE form. Hack away with AE until the Gorgon's done.

This achievement has been confirmed to unlock at two different spots. 1. At the stat screen after the small cutscene. 2. Right when you kill the Gorgon.