You reach out with your mind to another creatures mind, and sap their very intelligence, bolstering your own temporarily. 
When you target a creature with this spell they must succeed on an intelligence saving throw against your spell DC, on a failed save the target takes 2d12 psychic damage and their intelligence score is reduced by 2, your intelligence score is increased by 2, these effects last for 24 hours. On a successful save the target takes half damage and their intelligence score is not reduced.