My Day’s Undoing brew wasn’t terrible, but I think it needs more tweaking. Hangarback Walker feels more promising so far, but I’m not yet fully convinced that it belongs in the main deck. Hangarback Walker is fine in the grindy matchups, but it’s slow and the deck already has too many 2-drops.
I have a recommended WMCQ list below, but your choice should depend on the metagame you expect. If you expect a lot of non-interactive combo decks, Merfolk, Tron, and Affinity, then go for my build with more Master of Etherium and Steel Overseer from my previous set of Affinity videos. If you expect a lot of Kolaghan’s Commands, Twin, or Infect, then Masaaki Hitomi’s build from Grand Prix Singapore may be better. You could even consider adding a Day’s Undoing to the sideboard with the aim of bringing it in against decks like Jund or Grixis on the play. And finally, if you have the time to test Hangarback Walker yourself, then be sure to try it out—it’s guarded skepticism from me so far, but it might belong in the 75 after all. I just haven’t played enough games against enough different decks to be sure yet.
My Recommended List
After watching the Modern portion of the World Championship, I have some additional thoughts. Affinity was very popular, but no one played Day’s Undoing or Hangarback Walker. Since Jund and Grixis were not popular there, there may not be a need for those cards either. However, I loved Ghirapur Aether Grid in the sideboards of Sam Black and Paul Rietzl. I completely overlooked that card, but it seems good against Infect, the mirror, or Lingering Souls/Stony Silence. Taking into account the World Championship metagame developments, I would play the following list at my own WMCQ if I weren’t on vacation that weekend. It is similar to what Olle Rade and Pedro Carvalho have been playing to success on Magic Online lately. The final cards I put in the sideboard are all aimed at decks that were popular at Worlds: Illness in the Ranks vs. WB Tokens, an extra Spellskite vs. Bogles, and Tormod’s Crypt vs. Living End.