Just a casual Mill deck for tabletop magic. Not much is needed to take this to Standard play either, just the lands honestly (and maybe a few spells, but nothing that can't be replaced with Theros awesomeness). I've done some minor play-testing against decks listed on this site that have very high ratings and this guy seems to win more often than not.
Flexibility and Focus are the keys here. We don't want to mainboard cards like Mind Grind due to it's super-focus on mill and lack of flexibility. Other cards like Life's Finale are singleton because they cost so much to drop and there's more aggressively-costed cards available to us. It's still beastly to play, and affords us a very control-centric board-wipe, so a 2nd is placed sideboard for that reason.
A bit of an argument can be made for Wight of Precinct Six over Jace's Phantasm but let's consider a few things here. To start, the Wight could get big and swing a bunch and maybe eventually get through. However, the Phantasm has flying. Both are susceptible to creature-hate, but the Phantasm has a slight edge being able to fly (Think "Evasion" from the BREAD analogy here).
Something to keep in mind when playing any control deck. You have a focus on how you're going to win the game, a win-condition. In this deck, the win-condition is the opponent having zero cards in their library when they start their Upkeep step. Therefore, anything and everything that prevents you from losing first is doing its job. Consuming Aberration is not an ultimate win-condition, and neither is Jace, Memory Adept or Ashiok, Nightmare Weaver. All of these cards are big and threatening, but if they hit the field and do only one thing before they get hate, they've done their job; they've prevented YOU from taking that hate. In the case of the Aberration, if he takes a kill spell or a board wipe, or a Detention Sphere for example, you prevented that card from affecting you or a planeswalker. If Jace hits the field and mills for 10 before the enemy sends creatures in his face, or burns him down, you now have 10 more turns than your opponent! Let the 'Walkers die, or the Aberration, and save that counterspell for the enemies win-condition!
When sideboarding with this deck, we have a few options for the major categories of decks we may face. Dividing those categories between Combo, Control and Aggro we have our strongest to our weakest match-ups in that order. There are always going to be some sub-types within those archetypes, but thats the general idea.
Against Combo decks. We should have minimal trouble in Game 1 against a combo deck; essentially we want to counter-spell anything moderately relevant and kill-spell any creature that looks menacing. In Game 2, we have to consider what they're likely to play (or sideboard in/out in order to increase the odds in their favor). We know our weakest matchup will be quick aggro, so we will want to toss in Life's Finale and Mind Grind, most likely, and potentially Essence Scatter, or Devour Flesh just in case. We could do with taking out expensive-to-cast cards like Jace, Memory Adept, Blue Sun's Zenith or Karn Liberated, or cards that are super-focused like Glimpse the Unthinkable and Traumatize. The bottom line is we dont want to risk NOT having a cheaper, more efficient, answer in-hand when the time comes.
Against other Control decks. We tend to see two major types of Control, Planeswalker Heavy and Mid-Range focused. With the Walkers, we can take a risk by dropping out 3 Warped Physique, 1 Consuming Aberration and 1 Jace's Phantasm for a total of 5 spots. We will sub in 1 Curse of Echoes, 2 Mind Grind 1 Tamiyo, the Moon Sage and 1 Witchbane Orb. This is still just a baseline suggestion, as all Control decks are going to have different tools available in their sideboard. Against the mid-range type decks, we want to add in 1 Life's Finale, 2 Devour Flesh and the Curse of Echoes while subbing out Karn Liberated both Jace, Memory Adept and a Traumatize.
Lastly, against Aggro decks. We will want to make a major overhaul of our entire deck to make it as fast as possible to compete with the aggro decks! We want Devour Flesh, Essence Scatter and Wall of Frost as a minimum, and even potentially Life's Finale, Rise of the Dark Realms and Tamiyo, the Moon Sage. For the first 8 additions, we will want to drop both Jace, Memory Adept, Karn Liberated, 2 Blue Sun's Zenith, 1 Traumatize, a Glimpse the Unthinkable and a Thought Scour. Although they aren't necessary in Aggro match-ups, If we want to add the Board-Wipe, the Rise and the Planeswalker, Id recommend dropping the other two Glimpse the Unthinkable and the other Traumatize.
A note about the "Maybeboard." The Maybeboard is a compilation of other cards I consider to be extremely worth-while in a deck like this. Even though I have not included them in my final build does not mean I consider them completely unworthy of this deck, or its build; it simply means that They aren't as efficient in my Meta as the cards that have been included.
This deck was built for a friend and Ive yet to build it for personal use. The explanation and description is more for him (or anyone considering building this deck for themselves) than for myself. Lastly, know your own Meta before attempting to use someone elses creation. What I wrote above can only help someone so much before personal experience becomes the larger factor. Good luck!