This new-fangled spherical hat (with chinstrap!) is made of some sort of very light metal and adorned with runes. It is rumored to have belonged to Halaster Blackcloak (the Mad Mage residing in the Undermountain), though no one has been able to confirm this directly with the wizard. 

When you attune to it, you hear dissonant whispers that distract you when thinking and speaking, and you must make a Constitution save (DC 12) or the hat imposes disadvantage on all Wisdom, Intelligence, and Charisma checks made by you for 1d8 hours.

Regardless, while you are wearing it, you gain the following benefits:

• You can use the hat as a spellcasting focus for your wizard spells.
• You have advantage on Wisdom, Intelligence, and Charisma saving throws.
• Whenever you are targeted by a spell attack or effect that causes you to take psychic damage, you are resistant to that damage.

Notes: Advantage: Saving Throws