Far from being a saint, Desmond had always been an avid sinner. His pain, his loss, and the things he was forced to do to survive were only catalysts for that aspect of himself. However, no matter how much Desmond plunged into darkness, he never let himself fall into complete depravity. He knew that if he did, he would lose the only thing in his life that was still worth it; he would lose Claire.
Unfortunately, nothing stays the same forever, there will always be a first time for everything, and this was the first time Desmond had a taste of true depravity.
Desmond unleashed his lust with no emotion, no finesse. Desmond left his consciousness in a dark, secluded corner of his mind as he had sex with a parade of women with beautiful bodies but hideous souls. There was just so much pleasure to revel in that Desmond felt he might go crazy on more than one occasion.