This is a refinement of my previous Toshiro list, but that one's a couple years old at this point so I'm creating a new thread.
Toshiro is great value with removal, so the core of the deck is a reactive control build. Unfortunately we're working with mono-black, so our removal options are mostly limited to creatures, but we can play offense by recurring their creatures, and generate loads of value by double-casting draw spells.
Our wincon is a durable mix of recursion and tutoring. Sidisi + corpse dance lets us tutor repeatedly, XHD + corpse dance lets us recur repeatedly, XHD + rise of the dark realms gives repeatable reanimation of everything, and both Sidisi and XHD work well with the recursion we're already using for value.