(At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.) When Vexing Sphinx dies, draw a card for each age counter on it
Traveling Chocobo (Borderless Art, Pink Neon Ink) Mythic Rare, 511b Wait, another Chocobo
Its enters trigger lets you reveal the top 10 cards of your library and grab one card of each color pair, which can easily refill your hand with removal, utility, and threats
Chaos Defiler Chaos, the Endless Defiler of Souls Imskir Iron-Eater Kardur, Doomscourge Lady Orca Malfegor Master of Cruelties Ob Nixilis, Captive Kingpin Orca, Siege Demon Orcus, Prince of Undeath Rafter Demon Rakdos the Defiler Rakdos, Lord of Riots Rakdos, Patron of Chaos Rakdos, the Muscle Rakdos, the Showstopper Sire of Insanity The Balrog of Moria The Balrog, Durin's Bane The Balrog, Flame of Udn The Beast, Deathless Prince Valgavoth, Harrower of Souls
This is true even when a player elects to hold priority and take multiple actions in a row
Aristocrat classics are one of the best choices, with Zulaport Cutthroat and Blood Artist proving to be as good as ever in the vicinity of dying creatures