Soul Shard

You diablerized someone, and that spirit was strong enough to remain permanently active within your soul. It fights you constantly, and you can never be sure that its sentience isn’t influencing your actions. When your body is wounded, this spirit leaps upon the weakness and fights your control. While it tears at you from the inside, you must marshal your inner resources, lest the spirit forever take control. If you ever take enough damage to reach the Incapacitated wound track or beyond, you cannot spend Willpower until you are once more healed to the Injured wound track (or better).