Cyanide's Kiss

You place your hand on a creature. In the other you have a magic poison. You channel it into the creature acting a conduit. You feel the life escape the creature. In your other hand you see nothing but ash. 

The creature makes a con save DC 20. On a fail the creature dies instantly. On a success it is left with 1 D20 health+ its con modifier.

 The materials cost 1,000gp but pulling it from the stash destroys the stash. if you pulled something from the stash that long rest already and then pulled cyanide then it would explode dealing a 1/4 of your current hp and 6 d6 to anything within 5ft. 

The caster takes 1/4 of its current hp.