The crystal key is a powerful artifact that can be used to open any door, no matter what lock or barrier is in place. It is said to be able to even open the doors to other dimensions. The key is sought after by many, as it would allow them access to places and things they could never hope to see or obtain otherwise. Bloody battle refers to the often brutal and deadly conflict that arises when two or more parties vie for control of the key. Many have died in these battles, and it is said that the key is stained with their blood.