I have one really big problem with this deck! Where's Nicol Bolas, Planeswalker? If you are going for control or turning people against them nothing says that better than him! "Oh you played a Ulamog, that's cute. Now I played YOUR Ulamog! MWAHAHAHAHAHAHA!"

So I understand your theme, but I think you are going a little heavy on the theme and a little light on the execution. You have all these super expensive creatures with no way to cheat them out and not enough ramp in the deck.

Also just some card cuts I'd suggest:

• Thraximundar: Great commander, otherwise it's just too expensive
• Quicksilver Gargantuan: Just play Phyrexian Metamorph it's much cheaper and copies anything
• Prince Of Thralls: People will always pay the 3 life for any creature that is actually worth you bringing back
• Blood Tyrant: Too expensive
• Diluvian Primordial: I get it... But your assuming you're going to have a good target with this.
• Dragon Tempest: you don't have enough dragons to get value out of this
• In Garruk's Wake: Great card, too expensive, just run Damnation

Some card suggestions:

• Bribery: Just a better version of Primordial
• Disciple of Bolas: oh the flavor! Besides flavor, this is a solid card in your deck
• Wheel of Fortune: This is gonna be a much better card than Windfall because if you have no hand you still draw seven! Plus this can help you put a creature in the grave to Scarab God into play
• God-Pharoah's Gift: if you decide to play with all these high casting cost creatures the best way to cheat them out is grave recursion, and this is a free Reanimation every turn
• Liliana of the Veil: If you are going to play discard she is the best.
• Memnarch+Liquimetal Coating: Great combo and it would let you steal any permanent you wanted.
• Leyline of Anticipation/Vedalken Orrery: Since you are playing control, meaning you are holding up mana for turns on end, you should always be able to respond with any kind of answer including permanents not just counters
• MORE REMOVAL, LESS COUNTERS: what about the one time you tap out and you can't counter something? You need cards to deal with threats. Ex: Hero's Downfall, Vraska's Contempt, Doomblade
• MORE TUTORS!: You can't be a schemer(insert joker meme) without ways to make your schemes unfold when you want them too!

Just a few cards for ramp:

• Mana Crypt
• Mana Vault
• Mox Diamond
• Chrome Mox
• Fellwar Stone
• MindStone
• Hedron Archive

I agree with Fellwar Stone as well if you are not super attached to that draw effect from Commander Sphere. An extra mana a turn earlier is more helpful in a deck without a lot of ramp such as this. Instead of Cancel go with Dissolve for that sweet, sweet scry effect. Go with a filter land such as Cascade Bluffs, Graven Cairns, or Sunken Ruins instead of Temple of the False God. It's useless until at least turn 5 unless your have Urborg out.

Funny thing is, most of these cards were in here at one point.

I actually did steal an Ulamog when playtesting this deck a few days ago. This guy was playing Eldrazi tribal with Jodah, Archmage Eternal and played an Ulamog. Long story short, I stole it with Dragonlord Silumgar and milled them out.

Dragon Tempest is actually way good in this deck. When casting Bolas while tempest is out an opponent must discard their hand because Nicol Bolas did damage to them. To make matters worse Nicol Bolas has now gained haste.

I like In Garruk's Wake, I can kill all my opponents creatures and planeswalkers, while leaving my own board alone. I believe the cost is well justified.

Thanks for the suggestions! I will definitely take these into consideration.

@Darkshadow327 Maybe in your meta, but against another control deck or black/white deck or a deck with flying creatures you play Bolas and he's a dead card. I'm not a huge fan of cards that require combat damage because almost every deck runs removal, one good Path to Exile/Swords to Plowshares/Anguished Unmaking/Utter End/etc. kills that card before it ever does anything.

Also In Garruk's Wake doesn't prevent regeneration, and if you play with any green/black decks regenerate is a huge deal.

DrkNinja

I don't really have a meta, I play online on Untap. Things that kill happen, you just have to deal with it. The good thing about this deck is that it doesn't really put anything on the field, so I'm able to kind of lay low until I'm ready.

I forgot to mention, you should play Etali, Primal Storm

would Quest for the Nihil Stone work in your favor? There's also that legendary specter Urgoros, the Empty One that can also work.