Thought Vessel can probbally go, other than that the deck looks pretty solid.

If you were to change something about this deck, I would suggest to swap out the Theros Temples. A Scry is nice, but the land entering the battlefield tapped is setting you back so much in a deck where speed is the key to victory. If you do not want to pay a sack of gold and your kidneys for a legacy mana base, I would recommend the Pain Land cycle (Llanowar Wastes etc.) as these are generally cheap and effective.

The only thing better than sacrificing tokens to Prossh, is saccing your opponents creatures to Prossh. I like to run a lot of Act of Treason & Hijack type of effects to both deal with problematic creatures, and to fuel Prossh's damage.

I like the build, and write-up. +1. You can check out my build at That's so Prossh. I run more of a steal/sac build. I have 9 Threaten effects (3 Creature, 3 Sorcery, 2 Instant, 1 Planeswalker). Then I run 8 sac outlets (Including Prossh). It has been effective so far.

I understand your build is in a slightly different direction, but I would recommend Greater Gargadon, High Market, Bloodghast/Bloodsoaked Champion, Champion of Lambholt/Rogue's Passage, and Fulminator Mage/terastadon to get rid of Maze of Ith lands.

How well does Somberwald Sage, and Fecundity work for you? I've seen both in lists, and always feel like there is a better value card for the slot.

Talisman of Impulse and Talisman of Indulgence over Gruul Signet and Rakdos Signet? I've found them more useful.