Zhao, Ruthless Admiral is a flexible creature that can go into the red-black deck, and is especially synergistic alongside permanents that can sacrifice themselves like Clue tokens
It can be used both offensively and defensively (though a defensive Rift with no follow-up remains a bugbear for players everywhere)
This was the most popular of the four decks by far, and face Commander Ulalek was a big part of that
Polymorph by Samuel Leng Polymorph is generally not seen in Premodern due to Oath of Druids, Show and Tell, Natural Order, and Reanimate providing more efficient ways to cheat out creatures, but I like Samuel Lengs attempt
Being an instant also lets you leverage the ability by holding up countermagic, card draw, or bouncing your opponents board states to remove all blockers before your turn