This is my latest attempt to make mill competitive in modern. My previous version Attrition relied pretty heavily on the Duskmantle Guildmage+Mindcrank combo, which proved to be rather inconsistent, so I pulled the combo and chose to focus more on straight up milling.
Active Mill:
Archive Trap: Hitting for 13 at no mana cost is brutal, provided the opponent searches, but it's modern so there'll be fetches, plus the forced searches I'll outline later.
Glimpse the Unthinkable: Mill 10 for without relying on an opponent's searching their library.
Mind Funeral: Though potentially unreliable, this typically hits for 10+ with the ability to be crippling.
Thought Scour: Instant speed mill for 2 with the added benefit of card advantage.
Trap Enablers:
Ghost Quarter: Blowing up a land early game can really slow a deck down, forcing opponents to decide between taking a potential Archive Trap or giving me a board advantage.
Path to Exile: Similar to Ghost Quarter this puts opponents in a position to make a decision.
Scheming Symmetry: Still need to get my play set of these, but to force a search to hit Archive Trap as early as turn 1 on the play sets me up nice and early. Also, the turn 1 god hand of a source, Scheming Symmetry and 4 Archive Traps is too sweet a possibility.
Card Advantage:
Visions of Beyond: Draws 3 more often than not, helps keep my hand full
Thought Scour: Mill 2, draw 1 keeps the deck rolling nicely
Removal:
Path to Exile: Nukes a threat for good and can enable Archive Trap.
Fatal Push: Total value play, between fetches and Ghost Quarter it shouldn't be a problem hitting CMC 4s
Vapor Snag: Not sure if this will stick around, but having one drop removal in all 3 colors seems solid.
The Rest:
The man lands are there in case I don't have removal when I need it, Snapcaster Mage to flashback a Path, Push or Glimpse in a pinch and Hedron Crab for some extra mill off land drops.
Sideboard Tech:
Leyline of the Void, Rest in Peace: Main ways of dealing with graveyard recursion. Losing the extra draw from Visions of Beyond is a blow, but you can't let Zombies or Dredge get the upper hand.
Hero's Downfall: Walker removal
Stony Silence: Because mana rocks are annoying AF
Laboratory Maniac: Self mill if Leyline of Sanctity becomes an issue.
Open to suggestions on ways to improve and cards I haven't considered.