Whenever someone builds shirei and starts looking at all the 1-power black creatures, they have to make one very important decision - do I want to be a jerk? Because, out of the etb and death trigger creatures that fit into shirei's purview, many of the most powerful are built around one thing: making your opponents discard their hard-earned cards.
This deck is all about taking the jerk path. There's a bunch of ways to lock the other players out of the game, both on the board and in their hands. It's also built to be obnoxiously hard to kill, with tons of recursion and draw to keep your most obnoxious pieces coming back again and again.
Played this one more than most - I think 5 games. mostly because it kept not working at all. Partly my fault, it might be a bit too light on lands, and maybe all draw and tutors. Definitely part of it was just bad luck too, though, I don't want to make assumptions based on just a few games, but if I rebuild I'll probably throw in at least a few more lands, another draw engine, and another tutor or two.
I did have it go off once, when it went off pretty absurdly. T2 ravenous rats, with a questionable hand...then I get wheeled into sol ring + aetherworks marvel turn 3. Another opponent plays blood moon to totally shut down the other 2 players, but I'm MBC so I don't care...then I play shirei + fume spitter which I can use to "sac" my rats...so now I'm triggering discard and double energy every turn...I hit a sac outlet off marvel, and then oversold cemetery...and then grave pact...oh and I recur and play (from my wheeled hand) my smothering abomination so now I'm drawing 3 cards per turn...one of which is grim haruspex so now it's 6 cards per turn...around this point everyone's about out of cards from my black cat and everyone else scoops.
Overall this deck suffers from what a lot of decks do - it's either on or off. When it's off, it's boring and horrible. When it's on, it goes cuckoo bananas. Partly because Shirei triggers EVERY endstep, so in a big game basically any etb trigger or whatever will result in totally bonkers things. And then when it's off, it's just so boring because most of your 1-power creatures are utterly worthless without shirei. It's fun when it goes off, but it only needs to go off for like 1 turn before the game is basically over. That sort of hit and miss gameplay isn't really my favorite, and I don't think it's super fun to play against either - it's basically like a combo deck, except that the combo takes a little longer to win.
3/5. Amusing when it goes off, but not consistent, bad when it can't go off, and a little too powerful when it does go off.