This fun to play Rogue/Mill deck is based off of the challenger deck from Zendikar Rising. It focuses on milling your opponent to give your creatures buffs, mostly once they get eight cards in their graveyard. Merfolk Windrobber is a useful blocker, after they have seven cards in graveyard then you can just block then sac it to draw a card. Thieves' Guild Enforcer, Soaring Thought-Thief, and Ruin Crab, are our main mill engines, and Zareth San, the Trickster, can ninjitsu onto the battlefield to take your opponents best card that they milled. Nighthawk Scavenger keeps getting bigger even after your opponent has reached more than eight cards in their graveyard. Krydle of Baldur's Gate provides extra lifegain, mill, burn, and scrying abilities, and also synergizes well with Zarth San and Nighthawk. Drown in the Loch and Heartless Act are both excellent removal spells in this deck, and Drown in the Loch also works as an ideal counterspell, but again when playing combo or control decks, maybe sideboard Duress for Heartless Act. If you trigger Ashiok, Sculptor of Fearss ultimate, then that's pretty much game over, but most of the time you won't get that far. We mostly want ashiok's +1 ability, for card draw and helping to mill your opponents. Ashiok also serves as a distraction, making other players attack her instead of you directly.
This decks main weakness is against builds with lot of graveyard recursion, such as zombie decks. (My brother has killed me several times with Zombie Apocalypse).
I should also add that this can win by milling, but not often. Milling does often make my opponents nervous in longer games as they watch their library dwindlng down, but I most often win by combat damage.
