You should definitely be running
dismember in here, even though all your mana is black, using the phyrexian mana can let you control your life total and get to using shadow really quickly. Highly recommend
scourge of the skyclaves as another creature, I'd honestly suggest instead of the
Gurmag angler. If you're running mono black, you might want to add a little actual life control, maybe something that can conveniently gain a life or two, I don't know exactly what you'd want to work with there, but you don't have the increased aggro of rakdos/mardu/jund or the control of dimir/grixis/esper shadow, so you might want to have a little insurance to make sure you can't get popped, especially against burn