Modern has plenty of viable combo decks, and with its wide card pool, there are even a few that exist but haven't found the best version yet. Today's deck looks like it's getting close to an optimal version.
Once you have Mindcrank and Duskmantle Guildmage in play, all you need to do is activate the Guildmage and put something in their graveyard. Cards like Ghost Quarter, Slaughter Pact, Gut Shot, and Inquisition of Kozilek do that just fine. Meanwhile, Muddle the Mixture conveniently finds both combo pieces, which we've seen put to good use with Thopter Foundry and Sword of the Meek.
Aether Vial makes the deck feel like the various Cephalid Breakfast decks we've seen in Extended and Legacy, allowing you to sneak your Guildmage into play while still having open mana to protect and/or activate it.
This deck might have a ways to go before its taking down big tournaments, but this is a great start to a powerful shell.