RolledAOne

I agree. Why is Warden of Evos Isle in this deck?

What is the goal of this deck excatly? That might help people give suggestions.
I think for sure you should replace Obelisk of Bant with Darksteel Ingot or Chromatic Lantern.

Well you are in white, you should add in better removal like Path to Exile, Swords to Plowshares, Return to Dust, Unmake, ect. This would be better than giving a creature -4/-4 or whatever. It's also cheaper.

How many you want to add is up to you. Most people I've seen running this type of deck or Relentless Rats only run around 25 to 30. However yours you want to hit more with ripple so thats fine.

Ok cool. Yea each play group is different but if that player can exile your library down that far I don't think adding 7 cards from exile to your library will be much help at all.
If you can keep the mana up each turn Demonic Hordes could be useful. Eldarazi are always nice. I'd run them over that elixir anyday. They give you much more use.

Honestly I don't like modern much and I think its a bad format cause they ban most good cards so only a few decks can ever be played. Not trying to discourage anyone from playing it. I just went and rechecked the ban list and saw how much they took out.

Remove the two instants you have and put in Gravepact/Dictate of Erebos or those artifacts you mentioned.
Also what does Mirror of Fate do for you?

Board wipes to destroy all creatures and then use your commander to pick them all back. Black Sun's Zenith, Damnation, Decree of Pain, Life's Finale, ect. Those are so good wipes to help you regain control of the board.
Also you want to the mana ramp incase you an opponent stops you from using your Shadowborns. Then you can hard cast your demons if need be. You also need to have Cabal Coffers or Urborg is pretty pointless.
Add in some more tutors so you have a good chance of getting Stone out.
Patriarch's Bidding can help you get back your Shadownborns or demons.
Shirei, Shizo's Caretaker can also help you get back your Shadowborns if he stays out long enough.
You can abuse them more with a card called Conspiracy (choose Demon) then you can really search for any creature.

I play a good amount of EDH so I'm just passing on what I've learned. It's to you how you really want to run this deck.

I see what you are trying to do with this deck and it isn't bad. I would add more removal and wipes to help abuse your commander a bit more or try to add in some ramp. You are in black so Cabal Coffers + Urborg, Tomb of Yawgmoth with Deserted Temple should go in for sure.
With the Shadowborn + Stone combo add in Profane Prayers, good amount of damage for a small price.

Also Painter's Servant isn't legal in EDH.

I know what you are trying to do. I've seen this type of infinite combo a lot back in the day and even now obviously. However you need to have a back up plan. At least add in some tutors or a way to get Conspiracy out.

If you are adding black you might as well add in one of the black allies like Agadeem Occultist or Hagra Diabolist.

If anything you would be better off running Darksteal Ingot or Chromatic Lantern. Sea Gate Loremaster is amazing in ally decks too.

Best thing to ask yourself is "Does this card help me get to my win condition(s)?" Or "How useful is this card to me overall?".

Well everything is all cleared up and you learned something new so no harm is done.

Yes it will. How this works is you would cast Disrupting Shoal naming X as 1 (or any number that you can pay at the moment). Now the spell will be 1UU and the Gohei will kick and knock it down to UU cost. Does that make sense?

So if you have 5 mana open with Gohei out and you say I pay 3 for X. Now you will only have to tap 4 lands because Gohei takes 1 out of the X for you.

Yea I agree, you can't beat every deck type out there. Still this would be a fun causal deck to play in multiplayer or a team game if you have some buddies to protect you early game.

Manlands is just the name given to lands that can turn into creatures like "shock lands" are the name given to the Ravinca lands that deal 2 damage to you if you want them enter untapped or "buddy lands" for the core set lands that need another land to come into play untapped.

No artifact ramp? or in general you have no ramp at all and are sitting at 33 lands. Test me this won't cut it and you will fall behind real fast because you won't be able to play anything. Most EDH decks run 36-40 lands with 3-5 mana rocks/fixers/fetches.

I think you are on the right track for this type of deck but you are really missing out by not adding in the manlands from Zendikar. Also having Valakut is pointless, you will only ever get to kick that off 3 times and that is if you draw all 8 of your snow-cover mountains.
Mutavault might be a good add also.

Like Gothy said you are running 2 priest of Urabrask. Also you are in mono red so you should be running Valakut, The Molten Pinnacle (with Thespian's Stage and Vesuva combo too).
Godo, Bandit Warlord would also be helpful for getting out equipment.
There are more cards I could recommend to you but you might want to try out the deck a bit and see what works. Otherwise feel free to ask for more help I don't mind.