After you complete the quest "Prison Break: Over the Wall" you will enter Lockdown Palace and receive the quest "Prison Break: Try Not to Get Shanked." Your goal here is to Kill Mr. Shank, grab the PTD and free Athena. First you must make your way through the prison until you see the shower scene and begin fighting Mr. Shank. The key to fighting him is to stay far away (he's a melee fighter) and take his shield down with an electric elemental weapon. Once his shield's down, you can shoot him with a fire weapon and he'll be dead in no time. After he falls, pick up the PTD next to his body and fight your way to Athena's cell. The achievement unlocks the moment you hand the PTD over to Athena.