Brainstorm

When you cast this spell, you may change three of your known or prepared spells from your available spell list.

The newly chosen spells must still come from your class spell list and be of a level and spell slot you are able to cast.

However, as part of the cost of the taxing mental energy used in the casting, you must then "forget” two spells, temporarily losing the ability to cast them from your available spell list.

These changes to your prepared spells last until you complete a short or long rest.