Helmet of the Hammerhead Knight

Wondrous item, rare (requires attunement)
  Whilst wearing this helmet your peripheral vision extends behind you granting you a +5 bonus to initiative rolls. In addition, your sense of smell is enhanced; you have advantage on Wisdom (Perception) rolls that involve smell and you gain the ‘Shark’s Scent’ and ‘Blood Frenzy’ features.
  Shark’s Scent. As an action you can inhale, gaining blindsight to a range of 30 feet. This blindsight can only detect a creature that has blood and that does not have all its hit points.
  Blood Frenzy. As an action you can cast the blood frenzy* spell on yourself at will.
  Curse. This helmet is cursed with the essence of its former occupant, and becoming attuned to it extends the curse to you. As long as you remain cursed, you are unwilling to part with the helmet, wearing it even to sleep. Over the course of a week you begin to develop shark-like features. First your skin develops small patches of tough, iridescent scales. Next, your fingers and toes become webbed, and small fins appear on your elbow and neck.
  Lastly are the teeth. They become a jagged conveyor belt, a natural weapon which you can use to make unarmed strikes. If you hit with it, you deal piercing damage equal to 1d6 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike. When this occurs, the curse is complete and you are constantly under the effects of the blood frenzy.
  Casting remove curse or using similar magic ends the curse, but does not undo any changes to your appearance that have already occurred.