Sifu

In the 3rd level, The Museum, you fight your way up to the 4th floor. Once you defeat numerous rooms of enemies, you reach the shrine. You can head left (if you were floating in the center of the room looking at the wall) to a set of stairs back down to the 3rd floor. There is a female enemy standing there admiring a mask. Defeat her. (She drops the door code to the locked door in The Club. Nice.) Then focus on the mask she was looking at, press the X prompt, and the trophy pops. Random. Bonus tip: afterwards, go back past the shrine and hop the rail at the yellow arrow on the floor to get to the boss. Not obvious, I got lost for a while.