The four decks coming back are "Devour for Power" (helmed by The Mimeoplasm), "Built from Scratch" (the Daretti, Scrap Savant deck), "Wade into Battle" (with Kalemne, Disciple of Iroas leading the charge), and "Breed Lethality" (with everyone's favorite proliferator, Atraxa, Praetors' Voice)
With Doubling Season in play, Planeswalkers will enter the battlefield with double the normal amount of loyalty counters, and the curve is perfect: turn 5 Doubling Season, turn 6 play Teferi, Temporal Archmage, which will enter the battlefield with double the loyalty, and you can instantly get your emblem, which will stick around until the end of the game and just make things silly
Its controller mills three cards
Don't hope to dodge it forever, Nevermore it and don't worry about that card in their hand they never play