Id take out a forest for another chord of calling. You dont need 24 lands with all this ramp.

It seems good, but I think it might be trying to go a little too big, and that's coming from a guy who prides his version of the deck on going bigger than any other ones.

Maybe a few more early drops with double devotion like Swordwise Centaur . It can help set up an early devotion count for Nykthos, and gives the deck a few more aggressive starts. Also recommend dropping Polukranos and Nykthos down to 3 each, as while they are amazing things you want to see each game, multiples will just clog your draws, and there's nothing more annoying then an opening hand where your only lands are two Nykthos'.

Twingrove is good, but doesn't really benefit from Mana Ramp at all. Dropping him off from a Nykthos, three forests, and a few manadorks leaves you with a whopping pair of 3/3s. I recommend swapping with Hydra Broodmaster, a natural 7/7 for six, that can spawn an army with all the mana you can make.

Even with all the ramp, Hornet Queen and Phytotitan seems too high costed considering you're already running, with the list you have at the moment, Six 6-drops and five X-Spells. I might recommend either Arbor Colossus or Heroes' Bane . Colossus can block and survive pretty much any flyer in standard, and it's monstrosity can still kill one even without blocking. Bane, on the other hand, can get REALLY big with Nykthos in particular, and Nylea gives him the one thing that makes him unstoppable: Trample.

I'd also say look into Reverent Hunter . This three drop gets big, fast. The version I run other can drop him turn five as at least a 5/5. Get to the late game, and it's even more crazy. You could spend three mana and get a 12/12 or bigger out of it. I think I dropped him last FNM as a 21/21, with Trample thanks to Nylea.

Finally, I'd recommend looking into Setessan Tactics . Even in green, there will be a lot of matchups where your opponents got a sufficient wall to hide behind, or got some creature with a dangerous effect. Tactics can let all your creature you target with it basically tap to kill something, as 1-on-1, your creatures will likely be bigger than whatever they're fighting, clearing the way for some lethal attacks. Tactics has saved my life so many times against dangerous creatures that threatened to kill me, like Master of Waves.