Treasure Dredger
It has all sorts of combos, from loops involving the various Altars to mill or have infinite EtBs that ping opponents, to infinite mana generation via Zirda and Basalt Monolith for a burn spell, to using Arcbond and damage redirects to creatures like Brash Taunter, to the simple and satisfying infinite combats gained through Aggravated Assault with Feast and Famine or Reaver Cleaver
If your opponent has a proper sideboard made, you can count on them bringing in cards that will remove it
Opponents tend to underestimate this little artifact (I mean, it's just one card, right?) and keep playing their cards on curve until they realize you are wildly ahead in card advantage
Our second Expertise in a row, Yahennis Expertise will be a heavily played sweeper in black-based midrange and control decks, but -3/-3 isnt necessarily a reliable way to clear the battlefield
No player creates a Beast token