void harvest

A spell that cosumes your arm/arms in void when you touch a person/people it turns them to ash/dust and you asorvbe hp/mana i want it to be for warlocks but dnd beyond can change it if they want i don't care its up to them. you have to roll a d20 to use the spell with out it messing up and the target has to have low hp like 15 or 20hp im not sure. sry im new to this so they can take it down or rewrite it sry