Sander Cohen is another of Rapture's citizens gone mad. The psychopathic artist is in charge of the game's Fort Frolic level and is currently working on a quadtych that he refers to as his "masterpiece." Before allowing you to continue on your way toward Andrew Ryan, he requests that you hunt down four of his former "disciples" (Kyle Fitzpatrick, Martin Finnegan, Silas Cobb, and Hector Rodriguez), kill them, and snap photos of their corpses. These photographs will become the main pieces in his quadtych.

Finishing the work for him earns you Sander's respect and the Medical Expert 2 tonic as a reward. He stays true to his end of the bargain, too, reactivating the bathysphere so that you can continue on to Hephaestus. If you don't kill him in Fort Frolic, you'll meet up with him again in his apartment on the Olympus Heights level. Provoking his anger here will grant you access to a previously inaccessible Power to the People station and a couple of Xbox 360 achievements. In combat, Sander is more-or-less a Houdini Splicer with more health and a greater teleportation range. Once you've slain him, you can claim his muse key for the padlocked display case in Fort Frolic.