Your patron’s influence has affected you with a sickness. Your physical form is significantly affected by this illness. Perhaps it is a discoloration in your eyes, a deformation on your body, or a disconcerting scent on your soul.
Regardless, anyone who views you knows, deep down, that you are diseased. You have advantage on Charisma (Intimidation) checks and disadvantage on Charisma (Persuasion) checks.
As a Bonus Action, you can take 1d6 Necrotic Damage to have your disease flare up. You can then add the number rolled on the die to one failed Ability Check or Saving Throw you make before the next long rest, potentially turning it into a success. After adding this bonus, your disease mellows. You may do this a number of times equal to your proficiency bonus per long rest.