The last returning mechanic, Adventures, will arrive slightly different because these new cards will carry off-colour Adventure sides - including at least one multi-colour cost
Niv-Mizzet, Parun Niv-Mizzet, Parun does what Izzet likes most: It rewards you for playing instants and sorceries, or drawing extra cards, making it one of the best Izzet commanders and spellslinger commander, on top of featuring in Izzet's most powerful combo
This helps with quickly ramping up the number of cards in your inkwell , making it easier to play the high cost characters like Belle, Mechanic Extraordinaire, who can also be a shift target , as well as Lyle Tiberius Rourke, Crystallized Mercenary, who is not only a key damage dealer , but also pretty darn good at questing
Its even pretty great in flicker decks, to be honest
As the blog post explains, these cards were just getting played too much, and controlling the rest of the meta right now, as everyone else has to play around them