The goal of this deck is to start with NittanyLionRoar's Mono-Green Nissa, World-Waking, Stinging, & Eating green devotion deck and update it post-Khans rotation (dropping the Burning-Tree Emissary and bringing in some Khans cards) for use in Standard constructed.
The key ramp cards in the deck are Nykthos, Shrine to Nyx, Voyaging Satyr, Courser of Kruphix, and Nissa, Worldwaker. Elvish Mystic is an ideal turn-1 card, but once you've got two forests down you'd much rather play Sylvan Caryatid, so I've reduced the count for Mystics to two to make room for other goodies. This ramp skeleton takes up 22 card slots. Adding in 20 Forest as a mana base leaves you with 18 cards to make use of the tremendous mana reserves you'll find yourself with.
In its default configuration, this deck plays the archetype of the traditional mono-green monsters deck. Once you can afford to spend 9 mana on a creature (and in ideal circumstances this happens in round 4!), play Genesis Hydra as often as you can find it to dig through your deck for heavy hitters. The best options here are Hydra Broodmaster, Polukranos, World Eater, Arbor Colossus, and Hornet Queen. As your mana base grows seemingly exponentially, follow up with the other X-cost spells like Hooded Hydra, Mistcutter Hydra, and Crater's Claws (note that Crater's Claws requires red mana, so you'll need to have a Sylvan Caryatid, Verdant Haven, or Market Festival in play first and tap your land wisely).
However, be aware of one of the problems unique to decks that feature X-cost creatures that can be cast for ridiculous amounts of mana: huge vulnerability to damage reflection/redirection spells. Khans offers up a particularly menacing example in Deflecting Palm. I've lost several games to this card when I thought I was serving up the lethal blow. However, Khans also provides an excellent response card in the form of Stubborn Denial-- it's an instant counterspell for one mana with no option for buy-out as long as you control large creatures. Since our primary concern is the reflection of damage caused by large creatures, the spell is perfect in this deck. Sure, it needs a source of blue mana, but we have that in the form of Sylvan Caryatid (or Verdant Haven, and Market Festival if those get sideboarded in). Once you get Stubborn Denial into your hand, keep one of your mana-fixers un-tapped at all times just in case.
Another option to consider boarding in would be Aegis of the Gods, which makes you immune to burn and spell reflection as long as the creature survives (though it is subject to enchantment removal). This is probably a wise move if you know you're up against a burn deck, or if you know your opponent can build a lot of mana and has Crater's Claws.
You may notice that Rattleclaw Mysic is missing from this deck, despite being one of the most highly-anticipated green mana-fixers ever. At first, it did seem like a natural choice, but I can't find any situation where it is better than Sylvan Caryatid. The Caryatid is hexproof, is better on defense, allows me to splash any color I want instead of just blue and red, and I'm not planning on doing any attacking with the Rattleclaw anyway. Running a morphed Rattleclaw in place of a Caryatid in round two doesn't lead to a greater mana availability in round 3, even with the Rattleclaw's unmorph bonus (unless you specifically want to target a RUG tri-color 5-drop-or-less spell). If I'm missing some reason why the Rattleclaw is superior to the Caryatid for an early mana dork, please let me know. Otherwise, it's maybeboard for the Rattleclaws.
There are no other mono-Green cards in Khans that stand out as natural additions to this deck, so instead I concentrate on Sylvan Caryatid's ability to generate off-color mana (or Verdant Haven or Market Festival as needed) to open up the entire Khans card base to use. Crater's Claws is an X-cost red spell that works as an excellent burn addition to this deck, either as a removal spell for troublesome creatures early on, or a finisher when your mana capacity grows above the opponent's life total.
I need to play this deck quite a bit more to see where it is weak to get a better idea of what absolutely needs to be in the sideboard. In the meantime, here are some options for sideboarding into something totally different from what your opponent will be expecting having seen your game one deck:
Why not be ridiculous and ignore the heavy-hitting creatures in your deck altogether... board in Villainous Wealth and mill your opponent to death and/or beat them with their own cards all at once (note that because this card is a tri-color, it'll require either a Market Festival in play or two of any combination of Sylvan Caryatid or Verdant Haven).
Or, try turning this deck into a variant of Reid Duke's Wanderer Bard deck by adding in some Yisan, the Wanderer Bard, Kiora's Follower, and Prophet of Kruphix. With these three in play simultaneously, you can bring four creatures per turn into play and overwhelm your opponent quickly (note: the Wanderer Bard deck did a reasonable job against this deck in its vanilla form before I added the Hydra Broodmaster, the only way I know of to make more monsters faster than Yisan.
