So lets break down this:
Master of Cruelties - Our win condition. The idea is he leaves opponent on 1 life, and then something like Mogis, Chandra's +1 ability, or Rakdos's Return finishes the game
Chandra, Pyromaster- +1 to make some creature "blockless" so to say, so our Master of Cruelties could go by, or to finish the game if Master of Cruelties already attacked. +0 to dig for something useful in given moment, like removal. -7 isn't a thing in this deck.
Rakdos Keyrune- Sort of ramping and for chum blocking
Pack Rat -Alternative win condition if growed up to 4 or 5. Makes bad top decks good and synergies well with both Mogis, God of Slaughter giving the devotion and underworld connection giving a discard material
The rest is Removal and Discard.
Match ups:vs Burn : side
Staff of the Death Magus
and
Staff of the Flame Magus
for life gain. Magma Spray for
Chandra's pheonix
vs Control: side Pithing Needle for Planeswalkers and other annoying stuff and Slaughter Games for removing their win condition, most likely Elspeth, Sun's Champion and AEtherling
vs Grull Monsters: Lifebane Zombie can discard something like Polukranos, World Eater, Courser of Kruphix, Ghor-Klan Rampager or even Xenagos, God of Revels.
I'm open for every question and criticism