NivNiv Yorion

Control/Midrange hybrid that plays some of the best multi-color cards in all five colors. The new Niv (Niv-Mizzet, Supreme) gives the deck new life by giving all your two-colored instants and sorceries flashback. And since a lot of the premier removal in the format is single colors (Fragment Reality, Molten Impact, Go for the Throat, Wandering Emperor, Leyline Binding, etc.) and dodges all the Fatal Pushes like Niv-Mizzet Reborn, once you land one it will often stick around and give you great value. And while jump-start is not nearly as good as something like Flashback from Lier, since you have to discard to cast from the graveyard, it allows you to turn a useless Deafening Clarion into the Bind to Secrecy you need to stop the opponent from casting their Teferi, or a surplus land into another Lightning Helix to kill an opposing Crucias.

Feel free to tailor the sideboard to your liking. I think each card has its place, though you want to prioritize instants/sorceries if you can. A lot of Niv lists add Mystic Dispute, but I have decided to forgo it for Veto, since it is better against control and can be used out of the graveyard with Niv Supreme.