(Hemomancy)
You transform a portion of your blood into a poisonous substance. As you cast this spell, you must expend a number of hit points. You gain a number of temporary equal to the amount expended. For as long as these temporary hit points last, whenever a creature hits you with an attack while within 5 feet of you they become poisoned for 1 minute. A creature poisoned in this way makes a Constitution saving throw at the end of each of their turns, ending the effect on a success or taking 1d6 poison damage on a failure.