Unstoppable Slasher has been the staple of Mono Black Midrange decks for its value as a dual-purpose three-drop
The devotion mechanic is really strong in black with payoffs like Gray Merchant of Asphodel and enablers like Phyrexian Obliterator, Ayara, First of Locthwain, and Doomsday Excruciator, just to cite a few
If you do, Scion of the Ur-Dragon becomes a copy of that card until end of turn
Mark Rosewater digs into these categories in detail in his article "The Midas Touch." "Chinese Menu" Designs These cards take an effect that would be appropriate for Color A and one that would be appropriate for Color B and crudely glue them together onto one card
One neat trick to remember about is that you can cast it to destroy an Urzas Saga with its first lore counter trigger on the stack, which means your opponent would not get the chance to tap the land for mana
Fastbond often catapults its controller ahead by producing huge amounts of mana and landfall triggers