Blue/Black Mill
(Legacy)
60 cards, 8 sideboard
LANDS: 20
7 x {Swamp}
9 x {Island}
4 x {Halimar Depths}
CREATURES: 14
4 x {Silent Arbiter}
4 x {Nemesis of Reason}
4 x {Hedron Crab}
2 x {Dimir Doppelganger}
SORCERY: 12
2 x {Telemin Performance}
4 x {Mind Funeral}
4 x {Glimpse the Unthinkable}
2 x {Haunting Echoes}
INSTANTS: 8
4 x {Twincast}
4 x {Archive Trap}
ARTIFACTS: 6
2 x {Font of Mythos}
2 x {Howling Mine}
2 x {Spellbook}
SIDEBOARD: 8
4 x {Grindstone}
4 x {Painter's Servant}
Notes:
Win Condition: Mill Opponent's Deck
Alt Win Condition: Creature Damage
For extra opponent frustration, put the sideboard in there. The combo is an instant victory and will surely have your opponent seething with rage.
This is a solid mil deck, I would suggest a coulpe {Mirari}. Maybe sideboard a couple {Crumbling Sanctuary} as well.
How about {Jesters Cap} or {Traumatize}? I have a deck in the Commander section called Oona's Dictatorship that has some pretty boss mill cards. ☺
It looks like this deck could be in Modern instead of Legacy. I have a similar deck but I also have some {Tome Scours}. If you're using Crabs, I'd recommend throwing in some {Evolving Wilds} and similar fetch lands too. I've hit some people pretty hard with those Mind funerals too. :D
I might agree on sideboarding {Jester's Cap}s or something like {Relic of Progenitus} or {Tormod's Crypt} in case you run into graveyard shenanigans. Mill decks can be hosed by someone with an Eldrazi or two, so the Cap can help there.