Go ahead. Pet the kitty. It looks so friendly and its fur looks so soft. What could possibly go wrong?
Then suddenly you find a Demon ripping your soul out while holding out a contract that you don't remember signing. All you wanted to do was play with a cute kitten and now you're damned to spend the rest of eternity in fire and brimstone.
Don't worry. We all make mistakes.
I knew this deck would pop up sooner or later. Game-ending combos don't appear in Standard that often, so whenever one slips through the cracks, many players are all too eager to put on their brewing caps and make it work.
Most of the time the combo is too convoluted to attain the necessary consistency, especially in the current Standard dominated by aggressive creatures. But this one is lean, only two cards. One of those cards can dig for the combo, protect the combo by stripping answers from your opponent's hand, and buy time by gaining life and killing something.
Some lists I've seen take advantage of this by trimming on Harmless Offerings and playing a control gameplan, eventually executing the combo with the aid of many copies of Dark Petition. Not so here, as we see three copies of Harmless Offering. We're jamming and jamming hard, which I can certainly appreciate.
Between Duress and Collective Brutality, you have plenty of protection for the combo, and the rest of the deck is removal to buy time and Read the Bones and Tormenting Voice to tear through your deck as quickly as possible. It wouldn't surprise me if this list can win on turn 5 with regularity, using the first couple of turns to play disruption before sequencing Read the Bones, Demonic Pact, Discard + Harmless Offering on turns 3 through 5.
There aren't a lot of bells and whistles here. You could try to sideboard into a more traditional control deck if you expect your opponent has disruption for the combo, whether through discard or enchantment removal like Dromoka's Command, but doing so takes a lot of space, given how threat-light the maindeck is.
You also gain an advantage by making nearly all opposing removal bad. Even if they draw a Dromoka's Command or two, the additional time you gain by those cards not being able to pressure you should let you find the necessary discard to combo through them. The extreme focus of this list on the combo gives you a strange sort of inevitability. Unless your opponent can create pressure through your array of removal spells, eventually you are going to make them an offer they can't refuse.