When you cast a spell that forces a creature to make a saving throw, you can change the saving throw from Strength, Dexterity, or Constitution to another of these abilities, or from Intelligence, Wisdom, or Charisma to another of these abilities.
Once you use this feature, you can't use it again until you finish a Long Rest. You can also restore your use of it by expending a level 4+ spell slot (no action required).