You should put two of Mana Confluence it fixes Naya manabase more effectively also cards like Ajani, Mentor of Heroes and Thunderbreak Regent I would also up the lands to 24 makes it a bit better in not getting mana screwed cause mulliganing hurts this type of deck strategy Mastery of the Unseen could also be a 3 of sideboard slot to fit different cards I'm not so sure about Ainok Survivalist and Hidden Dragonslayer being good in your sideboard cause Reclamation Sage would be better and Arbor Colossus is pretty much doing the same thing and has the devotion and roadblocks ground guys instead of destroying them like the dragonslayer

First of all, thanks for feedback!

Mana Confluence could help, but i feel comfortable with mana base as it is now. red don't need to be rushed in any mean, and having white for Mastery of the Unseen is rarely a problem (thanks to Sylvan Caryatid). I don't like confluence all that much in non-aggro decks. Ajani, Mentor of Heroes is a good card, but I really don't want to run more 5 drops, as curve of this deck is higher than usual GW (devotion 4 dragonlords). Thunderbreak feels to me like "I have red, therefore Regent because it's too good", but I don't think he contributes to game plan of defending untill I can one shot with Nykthos, Shrine to Nyx and Crater's Claws. Reclamation Sage serve same role as Ainok Survivalist, and right now i want to test out if survivalist is better for this deck, since deck has a lot of manifest.

Sideboard is "in developement", as i don't really know what to bring, I need more playtesting. Probably some mix of Arbor Colossus, Banishing Light (Genesis Hydra can pick it up), Valorous Stance, Nylea's Disciple or Glare of Heresy.

Definetely only need Sylvan Caryatid. Rattleclaw Mystic is great and all but I feel like you don't need 8 creatures of mana ramping. Only four should be good enough. Could also cut down on the Genesis Hydra to two instead of four. And some Lightning Strike should go well to help with the early game. Also if you could give some feedback on my deck too (Grixis-Dragons) that would be cool!

MattN7498 Thanks for feedback!

First version of the deck had only Sylvan Caryatid as 2-drop mana dork, but I just feel like i need those 4-of Rattleclaw Mystic. Opening hand without a mana dork is unkeepable, deck is too slow without them, and with just 8 mana dorks (Elvish Mystic and Sylvan) you will get no-mana dork hands often. If that was typical Green based midrange deck, i would probably replace them with Lightning Strike, but honestly, in Devotion build based on Nykthos, Shrine to Nyx, creatures matter more. Espiecially when you consider that I'm manifesting a lot of cards with either Mastery of the Unseen or Whisperwood Elemental. Lightning Strike becomes dead card, while Rattleclaw Mystic can flip and gain me some life. Against most matchups this deck doesnt care what our opponent is playing.

Also, the more you play with Rattleclaw Mystic, the more you appreciate how potent it is. It allows plays like T3 elspeth or T3 Dromoka, as well as T4 Atarka.

About Genesis Hydra, I will test that, but from my expierience in G/R Devotion deck, you want this as a 4-of. If you draw multiple in few first turns, I can just play it for 4-5 mana and most of the times get a mana dork or Courser of Kruphix.