I think that one of the best symbols of Corey is what ends up killing him. The rock is a great symbol for Corey. Giles demonstrates himself to be as strong as a rock and as immovable as one in his defense of what he believes as right and honorable. For Corey, the rock represents what his spirit is in terms of believing that which needs to be followed, what should be as opposed to what is. I would say that another symbol that represents Corey would have to be a mirror. I think that Corey is the mirror that reflects what is happening in Salem. He is perfectly fine with reminding Salem of how they should be acting in the wake of the witch trials. He is a reflection of how corrupt and how divergent Salem has become from what they used to be. I think that Salem is an embodiment of what is wrong and a mirror can be Corey's symbol to represent how far off they have come. Salem looks at Corey and they should be able to experience how far they are from what they are meant to represent. For Corey, the rock and the mirror can end up being two symbols that embody his characterization.