Magical Contract

My group has entered into a magical contract to not be able to talk about an NPC in any way, shape, or form. If we do, we shall die of necrotic damage instantly. Also, if we run into the NPC, we have to tell the local guards where to find him. Our characters like this NPC and HATE the person who made us enter into this contract under duress but it was this or be executed. We also are not allowed to discuss the contract between each other or with other people. Anyone know of any ways to dispel this type of contract if we cannot get ahold of the parchment itself?