Recent articles by Israel Marques, Daniel Crane, and EDT have tried to classify Millstone and its place in the Magic Universe. None of them really got it right (well, EDT kind of did... But then totally ignored himself).
Marques states: "Therefore, Millstone (and cards similar to it, such as Grindstone and even Rootwater Thief and Denying Wind) can be classified as Total Option advantage cards because they eliminate a chunk of an opponent's Future Options, leaving them with fewer Total Options."
The Theory of Total Option advantage/disadvantage is interesting and in most ways sound - however, it is only useful as a tool for game play, not for deckbuilding. Can you calculate and work through all of the Total Options available during a game? If you can, then this theory may help you. If you, like most of us, can't, then we need a better way to gauge the usefulness (or uselessness) of Millstone.
Crane says: "Millstone is a Counter-Threat. It prevents your opponent's threats from hitting the table in the first place."
That Millstone is a Counter-Threat is only partially true; it does prevent some of your opponent's cards from ever seeing play - but it does a poor job of it, as you have no control over which cards it stops.
EDT writes about Millstone: "You are paying one card from your hand and getting nothing for it (because you don't win quickly, and it normally has no utility other than winning)."
This is the truth about Millstone, it is a THREAT, but EDT shines a very demeaning light upon it because "You don't win quickly." Since when has that been a requirement? Sure if you can't win quickly you better have a way to survive the early onslaught from the decks that CAN win quickly but there is no rule that says, "Thou must win the game as quick as possible"; Stasis proved that.
Millstone is a THREAT - it puts your opponent on a clock, not a fast, "Two-Headed Dragon with ten lands untapped" type of clock, but a clock none the less. Once Millstone hits the table, you have eighteen turns to do something about it or lose (fifty-three cards in the library at three cards per turn). Eighteen, did you realize it was that few? I didn't until I actually did the calculation. That means if you are playing Millstone, you need to do three things once you get a Millstone on the table:
1) Use the Millstone
2) Keep the Millstone in play
3) Keep your life above zero.
You need to do this for eighteen turns. You don't have to worry about punching through your opponent's defenses or keeping his life total in check. Just keep the Millstone on the table, use it, and stay alive. Let me re-iterate that: just keep the Millstone on the table, use it, and stay alive.
Maybe you're thinking that the same thing can be said about a creature? Just keep the creature on the table, use it, and stay alive. With creatures, you need to worry about getting the effect (the damage from your attack) through. Your use of the creature can be prevented in many ways: Blockers, damage prevention, fog effects. The use of the Millstone cannot be prevented.*
EDT said a few more things - one that is true, and one that I hope to prove isn't.
"Why could old decks (like Pro Tour 1 decks) use Millstone? The reason is that those decks were creatureless (or had creatures that were impossible to kill). ... The deck with only Millstones and no creatures isn't viable right now."
I disagree, I think a deck without creatures IS viable right now, and I am willing to put my money where my mouth is. (Is it me, or does that expression lose a lot when read instead of heard?) Let's rebuild my Dueling Grounds deck from my last article with the following tenants.
1) Each card must perform one of the three needed functions (Keep Millstone On The Table, Use It, Stay Alive.)
2) The deck must be creatureless, or contain creatures that are nearly impossible to kill.
Deck List from previous article, annotated with reasons:
4x Dueling Grounds (Stay alive)
4x Sterling Grove (doesn't fulfill criteria toss)
1x Story Circle (Stay alive, increase to four)
3x Rout (Stay alive)
3x Wrath of God (Stay alive)
4x Prohibit (Keep Millstone on table, Stay alive)
1x Misdirection (Keep Millstone on table)
1x Harsh Judgment (Stay alive Red specific so Sideboard)
1x Ivory Mask (Stay Alive, Discard, Red Specific so Sideboard)
4x Enlightened Tutor (doesn't fulfill criteria toss)
2x Millstone (Use it, increase to four)
2x Tidal Kraken (Ya think? Okay, they're history)
1x Heroes' Reunion (Stay Alive? Questionable relegate to Sideboard)
2x Orim's Chant (Stay Alive)
1x Elfhame Sanctuary (Stay Alive, Millstone specific so Sideboard)
1x Treva's Charm (marginally Stay Alive so toss)
2x Treva's Ruins
4x Kor Haven (Stay Alive)
2x Coastal Tower (too slow change to Adarkar Wastes)
2x Elfhame Palace (too slow change to Brushland)
So the Deck now looks as follows:
4x Dueling Grounds
4x Story Circle
3x Wrath of God
4x Orim's Chant
2x Treva's Ruins
4x Kor Haven
2x Adarkar Wastes
Now the only green in the Deck is for Dueling Grounds and the Sideboard. Is it worth it? I think so, but it definitely modifies the Mana base. So the lands are now:
3x Treva's Ruins
4x Kor Haven
4x Adarkar Wastes
We now have eight spots left, so let's add:
4x Counterspell (Keep Millstone on Table, Stay alive)
4x Fact or Fiction (Stay alive, Keep Millstone on Table, Use It)**
Now how about the sideboard?
From Original Deck:
1x Harsh Judgment
1x Ivory Mask
1x Elfhame Sanctuary
1x Heroes' Reunion
4x Disenchant (Elfhame Sanctuary is Bad)
4x Teferi's Response (Rishadan Port was a problem for the original build)
3x Tangle (Backup for Kor Haven.)
All that remains now is to test this new build and see how it does. I'll let you know how I made out, but please feel free to test it yourself, you may be surprised at how viable*** Millstone is.
Tidal Kraken is NOT tech.
* - Okay - I realize that Bind from Invasion will stop the Millstone - but c'mon, even "He who tried Tidal Kraken" realizes that Bind is not a good card.
** - Fact or Fiction actually does none of the three, but it allows you to get to any of the three, so it passes.
*** - Or you may come to realize that I have no idea what I am talking about and EDT was right, it isn't viable; but I am sticking to my guns on this one. It's viable.