When you cast a Wizard spell, you can also choose to un-prepare a Wizard spell that you have prepared. You can't use this feature to un-prepare a spell that you always have prepared. When you do so, you gain one of the following benefits of your choice.
Advantage on Spell Attacks
You have Advantage on spell attack rolls you make as part of the spell.
Impose Disadvantage
One target of the spell has Disadvantage on saves it makes against the spell.
Advantage on Saves
You have Advantage on saving throws until the start of your next turn.