Energy Transfer

You touch a creature of your choice and transfer some of your life energy to them. You take necrotic damage equal to 1d6 + your spellcasting modifier and your hitpoint maximum is reduced by the amount of damage taken until you finish a long rest. The creature regains a number of hitpoints equal to the damage taken. The damage taken cannot be reduced in any way.

At higher levels: The damage you take increases by 1d6 when you reach levels 5 (2d6), 11 (3d6), and 17 (4d6).