• Ahn-Crop Crasher saw a lot of play, you should definitely include it.
• Play at most 1 Deflecting Palm. It's not really good when the opponent expects it.
• Don't play Thrill of Possibility. You have no synergy with it.
• Funny thing with exert mechanic is that if you exert same creature multiple times in a turn, the creature won't untap only once. Hence play cards such as Response / Resurgence which give you an extra attack.

• Since you are playing Arbor Elf, Old-Growth Troll and Utopia Sprawl, you need to be 100% sure that you have Forest in your opening hand. You are now playing 12 Forests, which don't guarantee that. I would suggest that you go up to 16 at least.
• Aspect of Hydra is not a good card in your build. It works well only in a mono-green deck. Remove them. Ghor-Clan Rampager is a better pump and also a good creature with trample.
• Commune with Nature is a bad card. If you want a better alternative, play Once Upon a Time, but best would be to play none of it - it's only relevant in combo decks.
• Trample works well with Deathtouch, since you need to assign only 1 damage to each blocker and the rest to the player. Try 1 Bow of Nylea and 1 Basilisk Collar.
• Return to Nature is a situational card which may end up dead in your hand. Such cards are not to be played in main deck, only in sideboard.
• Don't play Thrill of Possibility. You don't have any synergy with it. Instead of spending 2 mana to get to cards you want, play cards you want.
• Colossal Rattlewurm is a 6/5 trample for 4 mana with some upsides. Play some 2 Ramunap Ruins instead of a Basic Mountain to support it.
• Explore is questionable. I suggest you remove them. Add extra Arbor Elf and you have one free slot.
• As was already mentioned, 1 Stonebrow, Krosan Hero should make it into the deck.

You missed the most obvious helix of them all - Smiting Helix

• Fill in the format. I suspect Vintage, since you are playing Demonic Tutor.
• What is the budget? If there is none, go with Badlands, Mox Ruby instead of 1 Simian Spirit Guide
• You are playing just 1 blue card, and it's not that much relevant - Windfall. Throw it away and you can then go two-color with much more stable and less painful mana-base. Remove 4 Aether Hub and 4 City of Brass. Play instead 1 Blood Crypt, 1 Raucous Theater, 1 Graven Cairns, 1 Sulfurous Springs, 4 Blackcleave Cliffs
• Memory Jar is an insane card in this strategy, since it causes your opponent to discard 7 cards while it gives you more cards to play. I would replace it for 1 Howling Mine. Jar may well be a reason to still play blue - for Tinker. In that case also replace a few swamps for Vault of Whispers.

• Playing 4 Dauthi Voidwalker together with 4 Tarmogoyf seems like an anti-synergy
• Mishra's Bauble works well with your Goyfs, Sheldred, Fatal Push, Molten Collapse. Play 1 or 2.
• I would expect 1 surveil land to fetch in a longer game.

• Don't play Ornithopter, it does nothing for your game plan.
• Roiling Vortex also works with Personal Sanctuary. You may want to add one or two.
• Board the Weatherlight doesn't work for you. Cards that you are interested in are not Historic.
• You have a lot of mana intense cards, and as such you need some mana acceleration. You may add some Knight of the White Orchid or Loyal Warhound. They work well with your Path to Exile. Or you may go the other way with acceleration - Gemstone Caverns decrease your hand size which is fine with Ensnaring Bridge.

1. Play 4 Reflecting Pool. Works great with Vivids and Primal Beyond. No need to play Prismatic Omen.
2. Supreme Exemplar is not very good. It works only with Incandescent Soulstoke.
3. Horde of Notions is the best card you have. You should be playing more of them, most likely 4. If one is answered, you drop a second one. If not answered, he'll overtake over the game.
4. Play more lands. Your deck is mana hungry, and even with Smokebraider you always have expensive things to cast or activate Horde of Notions.
5. I would replace one Island with Mystic Gate. You have white and blue spells with double mana and this filter will help you casting them.

1. Don't play Borderposts. They offer no benefit for you, but opponent may destroy them with artifact hate. You also risk having an opening hand without basic lands, making them unplayable. Play Arcane Sanctum and Jungle Shrine instead.
2. Add 2 Elspeth, Knight-Errant. It gives you an evasion against repeated blockers such as Sprouting Thrinax and also can itself provide repeated blockers. The +3+/+3 bonus doubles with Rafiq and Finest Hour.
3. Your sideboard is bad. There is no reason to play Call to Heel when you can play Hindering Light. You don't have any enters-the-battlefield effects, so you never want to return your own creatures to hand when you can leave them on the battlefield. You have no answer to the Martial Coup.
4. Check Cascade - Shards of Alara Block - an actual constructed deck from that era. It would destroy you hard with all the card advantage. Your deck also has problems with instant removal, since you always attack with only one creature.

1 Yawgmoth's Will as a tutor target is a classic - play some rituals, lotuses, play tutor for Will, replay rituals and lotuses, replay the tutor but now you have more mana.

If you actually playtest the deck, many times your hand is not that great.

1. 8 of your tutors put the card only on the top of your library rather than into your hand. I suggest you play Demonic Tutor rather than Imperial Seal.
2. You have problems with color fixing. You end up being unable to play your cards because you don't have right combination of mana. If your plan is solely to play only one turn, then Lotus Petal is better than Mox Jet or Mox Sapphire.
3. With Dark Ritual and 8 Lotuses, It's reasonable to get to 5-6 black mana. Some 2 Ad Nauseam and/or Yawgmoth's Bargain would improve your consistency.
4. Ceremonious Rejection looks bad. If your only plan is to play for one turn, play Pact of Negation. You'll save 1 mana and have more possible targets. It's better if you start the game. If your opponent starts the game, Ceremonious Rejection only works if you have Leyline of Anticipation. And if you have that, you should able to win even with Pact of Negation trigger.
5. Play 4 Gitaxian Probe and 4 Street Wraith. Your deck doesn't care for life, and you need to get your relevant cards.
6. If you are allowed to play 4 Black Lotus and 4 Blacker Lotus, then I assume anything is playable. If so, you forgot to include the most powerful card in the entire history - Contract from Below

You need to add some win condition. Even after gaining an infinite amount of life, your only threat are a few creatures. If the opponent eliminates those with Pacifism and similar effects, you will deck yourself.

You will need to remove 18 card to get to 60: - 2 Mystic Forge and 4 Deadly Dispute - Affinity is an aggro deck; it wants to put additional creatures on board, not just draw cards. You may leave Thoughtcast and Thought Monitor. That will also rid you of black color entirely. - 4 Mistvault Bridge - 22 lands is too much for a 60 card deck that mostly plays free spells. You also don't want to draw multiple tapped lands. - 2 Shrapnel Blast - You don't want multiples in your opening hand, because then you won't have enough artifacts to cast your spells. You are also playing another sacrifice outlet (Arcbound Ravager) and too many sacrifice effect have diminishing returns. - 2 Myr Enforcer - You were playing 12 7 mana spells, that's simply too much. You can't keep opening hand with 4 of them. - 4 Lotus Petal - The only card in your deck that was not Modern legal. Also it's useless in longer game.

After these cuts, your deck has 60 card. However, 10 of them are non-artifacts, which may be more than you would like.

I will also give you a few other tips: - If you are too low on 0 mana cost cards, try Memnite or Welding Jar. Jar does something even in longer game, unlike your original Lotus Petal. - Nettlecyst - Acts similarly to the Cranial Plating, but comes with a body and has a good toughness. If you would play it, I suggest that you replace them for Arcbound Ravager, as they are doing opposite things.