DedWards

Honestly, other than what I see on this site and the Reconstructed articles, I don't see much of other people's decks. I prefer to build from scratch. Surprisingly, I've found that I sometimes come up with stuff that's already done, though in a slightly different way.

Gitaxian Probe lets you look at their hand and draws you a card.
Surgical Extraction lets you look through their library.
Remand lets you counter the spell, then call its name with the other cards.
Lantern of Insight lets you see the top card of their library.

If that's what you're aiming for, this is a pretty good build. Countrol isn't exactly my strong suit, so I doubt I can be of much help.

At 4 mana, I wouldn't run more than 3 Valor in Akros. A Spear in the 4th's spot seems good as it provides more devotion than Valor and can be used as removal.

Archangel of Tithes would be awesome in here. Besides it's awesome limiting ability (that is borderline broken, in standard at least), it's a 3/5 flyer for 4 mana, and it also supplys 3 white to devotion. I can see it replacing Wingmate Roc.

Raven's Crime is a reusable discard spell.

Psychic Possession looks like it could be fun along side Sphinx's Tutelage. Another one that'd be fun with the Tutelage is Teferi's Puzzle Box :p

Valor in Akros

You could run a set of the Urza lands (Urza's Mine; Urza's Power Plant; and Urza's Tower) for in case your Amulet and / Chalice is not in play.

Ophidian Eye or Curiosity on Niv-Mizzet, the Firemind turns your deck into a machine gun :P

Ophidian Eye or Curiosity on Niv-Mizzet, the Firemind turns your deck into a machine gun, and in Commander that's an easy win.

I've always wanted to make an exalted deck using Bramblesnap. Attack with Bramblesnap, it gets +1/+1's from all the exalted triggers, then tap all other creatures to Bramblesnap's ability for even more +1/+1's. Knotvine Paladin doesn‘t have trample like Bramblesnap, but it's bonus +1/+1's don't require you to tap your own creatures, plus Trample it easily granted via cards like Selesnya Charm and Rancor.

I've seen Silent Arbiter used in exalted decks to limit the number of attackers and blockers, but I think Archangel of Tithes might be better at the role.

Can't say I'm a fan of Animist's Awakening. You'd need at least 5-7 mana to get maybe 2 lands off of it (on average), that's horribly under preforming. It could be good, if you're lucky, but I'd rather not dedicate 4 slots to a "could be". I'd rather run Nissa's Pilgrimage. Sure it can only fetch basic forests, but it's a reliable 1 on the battlefield and 1 in hand (2 with an unlikely Spell Mastery); and luckily you're heavy green. I run a 4/2 split of Nissa's Pilgrimage and Explosive Vegetation, but I can see a 3/3 split working too.

Additionally, for a landfall themed deck, you're light on the number of lands. I'd knock the number up to at least 23, preferably 24/25.

Lastly, I've been running a mono green land ramp deck in Standard for the last few weeks and Nissa, Vastwood Seer // Nissa, Sage Animist has helped a lot. First, she fetches a forest as her ETB effect (puts it in your hand though); is easy to flip (flips on your 7th+ land entering, fetches excluded); and her +1 either 'draws' you a card (a welcome ability in green) or gives you a land (triggering landfall). Her -7 is just a cherry on the cake.

Ya, it looked a little slow to me, that's why I suggested it. Also, it just hit me, depending on how heavy you go with the enchantments, Ethereal Armor is a must. Hopeful Eidolon is another nice 1 drop, early game it's a 1/1 lifelinker, mid/late game it bestows to grant lifelink (though you're unlikely to bestow it in a deck full of lifelinkers).

If you can get them, I think Birds of Paradise would be a better fit than Sylvan Caryatid. It may not have hexproof like the Caryatid, but it does come out a turn earlier and has flying, which works nicely with the Ascendancy's +1/+1 triggers.

I really like Young Pyromancer's synergy with Sprout Swarm (more free creatures to convoke with). Monastery Mentor does practically the same thing.

Impact Tremors and / or Purphoros, God of the Forge is another possible win condition.

Fling / Soul's Fire also works off the Ascendancy's +1/+1 triggers.

Time is relative

Also, Cruel Feeding is cool because it can target more than one creature, though be it at an extra cost per creature beyond the first.

Also, Cruel Feeding is cool because it can target more than one creature, though be it at an extra cost per creature beyond the first.

Sudden Spoiling is an awesome card on its own, but sadly, it does nothing with Horobi's ability as Horobi requires the creature(s) to be targeted an Sudden Spoiling doesn't target the creature(s).

Empty the Pits is an interesting choice, but with Horobi's ability, I'd have expected to see Ghastly Conscription.

Spells like Gild won't have their extra effects happen while Horobi is out as once you target a creature, Horobi's ability will kill it and your spell's target is no longer there. Because of this, 1 and 2 mana instants like Tainted Strike and Sorin's Thirst become cheap kill spells with Horobi out.

You may want to look at including more creatures that don't stay dead, like these:
Bloodghast
Akuta, Born of Ash
Bloodsoaked Champion
Nether Traitor
Any creature with Undying
Any creature with Persist
Any creature with Unearth

The options aren't bad, but like I said on your deck, we had different end goals in mind when designing the deck. I am gunning for the infinite combo, where you went for more reliable 'if I don't get it's build.

This looks like it runs more like a RDW that contains a combo, while mine is more of a combo deck that uses burn to buy time. Still a good deck, we just built our decks with different main goal.

I've often been sceptical of Blood Moon outside of mono red. It also shuts down your non basic lands...