Permafrost I actually recently tested this deck in a 5 player game, and learned that a lot of what you are saying is correct. Currently, this deck performs amazingly well, BUT there is no closer. I'm unable right now to take advantage of the lockdown and capitalize on the victory. I added in Sword of Body and Mind but find it rather difficult to obtain things in such a large pod. Granted, stax is typically better in groups of 2 or 3, but it gets the job done quickly when needed. The hardest part is finding a way to close the game out (Besides Earthcraft + squirrels nest) Which I find to be eventually added to this deck as a way to close the game off. I considered running Vitalize and Craterhoof Behemoth as a way to close out with Earthcraft but have since failed to produce results. Earthcraft needs to go into this deck before I can test this deck with a 8 drop slot.

If you wanted to go combo for the win, you should add a tutor or two. I really like Sidisi, Undead Vizier because she is a great blocker with deathtouch. Another great option is Diabolic Intent. You could add these and then just tutor up your Helm of Obedience Leyline of the Void combo. If you're playing in bigger pods, I would cut single target hand hate like Thoughtseize and maybe Hymn to Tourach. Amulet of Vigor doesnt seem to have a spot in this list either, if i counted right, you only have 3 lands the etb tapped, and two have a chance of NOT coming in tapped. You also dont have any Kismet effects that make your lands etb tapped and it doesnt help you untap more lands from Winter Orb effects. That in mind, if you CAN untap more lands with said effects in play, you can gain a huge advantage over the table, So Garruk Wildspeaker can help you untap lands and can be a win con with his overrun ultimate. He also makes big tokens if you really need them. Arbor Elf is another good choice, and you are a lucky bastard who has a cradle, so you can go nuts with mana.

Permafrost Orb of Dreams is a huge play maker in this deck with Amulet of Vigor effectively slowing the game to where i gain massive advantages. Sidisi was originally in my list of cards to add to this deck and may still get into the deck. I may remove Thoughtseize as it has done its job in the prototype of this deck, and can now be removed. Amulet/Orb is something that helps me out with the placing of a Golgari Rot Farm in the deck (to be announced). This weekend I'll be implementing a new card or two into the deck, mainly from my sideboard into mainboard. The Abyss and Nether Void make there way into the deck now. Along with this, I'm throwing in Torment of Hailfire as a win condition. Hymn to Tourach is extremely beneficial when playing the political game (like my LGS does) but I definitely see where it can come out. Especially if I want to play cards like Mind Twist some time in the future. Mind Shatter will be hitting this decks mainboard tonight as well to cripple big threat decks.Garruk Wildspeaker or Nissa, Worldwaker? I think Nissa wins a place in this deck over Garruk as she can fetch the basics (If i dont already have all my basics in play) I find that I should be adding an effect like Seedborn Muse into the deck as well to gain advantage over the board in stacking.I did consider Epic Struggle for this deck, however felt it would be too slow. With the mana acceleration, I also considered Omnath, Locus of Mana as a hard beater but determined that he was more of a situational card that does nothing for the mana that he hordes. It's been determined that this kind of deck does not like to leave mana open during players turns.
Arbor Elf why remove Arbor? It untaps a forest that may be needed to get pieces. It actually helped me win a game last night. lol (I was land screwed)

I missed Orb of Dreams when I talked about amulet, whoops. I would still pick Garruk Wildspeaker over Nissa anyday. Nissa only untaps forests, and her ultimate is way harder to achieve. Her first ability makes your lands more vulnerable, too, and in a stax list, I would much rather have a disposable 3/3 than a land creature. Garruk can untap Cabal Coffers, Gaea's Cradle and plenty of other abuse-able lands. Arbor Elf has the same effectiveness, and I would NOT cut him. I really like Torment of Hailfire in this deck, seems like a great choice.

Permafrost Yeah man, I completely edited this deck to add new things in earlier. I am really happy about the tests that I did last night with this deck and the additions. Sadly, Torment of Hailfire got countered in game last night, or I would've won. Darn pre-con won the match cause he ramped up so hard.