Story related. You will earn this on your Bad Karma playthrough.
After convincing the rebels to side with you in "Transference of Power", you will move on to the next story mission "Storm the Fort". In it you, with the help of the rebels, storm a fort in order to gain access to the Transfer Device. Once you get to the device you face a big decision of which of your two female companions you want to side with and ultimately gain their powers.
For this trophy you need to side with Nix and as a result will gain access to her Fire powers for the rest of the game.