Vahn’s Sympathetic Drain

When you cast this spell, one target humanoid creature within range makes an intelligence save. On a successful save nothing happens. On a failed save a magical tether links you and your target until the spell ends. For the duration both you and your target subtract 1D6 from all weapon attack rolls. While concentrating on this spell, the caster has a penalty equal to the number of creatures to concentration checks to maintain the spell.
At higher levels: for each spell level, the number of targets that this spell can affect increases by 1.