doctorhydrogen

Caged Sun and/or Gauntlet of Power I'd guess.

My variant: http://www.mtgvault.com/doctorhydrogen/decks/talrand-sky-summoner-edh-3/

Infinite combos are fine for the most part. Easily tutored infinite combos that require a one mana aura is going to get you hated out at any place I've ever played simply for wasting everyone's time. But by all means, throw together a Niv Mizzet the Firemind deck filled with Curiousity, Ophidian Eye, etc. and see how many high-fives you get every time you dump and aura on him and win on turn four.

Like I said, if that's your idea of a good deck just roll Maralen.

Pyscosis Crawler causes a loss of life. Curiosity and Keen Sense trigger on damage, which isn't the same thing, so there's no infinite combo.

But even if there was I'm not sure going "I win" because you happen to draw a 1 cmc aura is remotely in the spirit of the game even if it did work. At that point you may as well just run Maralen, Ad Nauseum, Sickening Dreams and 96 swamps.

Granted Curiosity and Keen Sense are cheap to cast, but they set up you for a 2-for-1, and they'll only get you a single card. I'd much rather run Bident of Thassa and Coastal Piracy in those slots.

There's way, way, way to many indestructible Theros gods these days for Naturalize. Deglamer or Unravel the Aether are IMO much better choices.

Nature's Will absolutely KILLS in Edric decks. Tap out playing stuff, attack and draw six cards, untap all your land, play stuff again. It's become the number one kill target for my opponents in my meta, and it's so good that I run Bear Umbra and Sword of Feast and Famine to have more land untappers.

Druids' Repository can generate a ton of mana in this kind of deck.

Recurring Nightmare is banned in EDH.

Arena is better in theory but in practice I could never make it work. It doesn't tap for mana so it essentially means you're only running 32 lands (I wouldn't run less than 35 myself), it costs four to use, and the opponent can pick the target. Triangle of War would be a better bet if you want a re-useable fight effect.

There are plenty of easier ways to kill a land than Blight. I'd start with Strip Mine.

There are so, so, so many indestructible artifacts and enchantments floating around right now (Theros gods, Darksteel junk) that I don't even bother with non-exile or non-tuck removal, especially in green. I'd run Deglamer and Unravel the Aether all day over Artisan's Sorrow and Emerald Charm. Tucking someone's Aethros or Nylea or Sharuum or Senn Triplets is invaluable.

Maelstrom Pulse can hit more kinds of things than Befoul, costs less mana, and if you use it to hit a token it will wipe them all.

Putrefy costs one more than Doom Blade but can hit anything AND can hit an artifact if you need it.

Ratchet Bomb is a one-mana reuseable board wipe of all tokens.

Since you're already running two efficient counters in Damnation and Supreme Verdict, I'd slot in something like Black Sun's Zenith over Wrath to deal with the guy running 3 Theros gods in his Tajic deck. There's so many indestrutibles these days that I'm not comfortable without at least one wrath that can handle them. Something like Terminus or Merciless Eviction that tuck/exile would work, too.

For the same CMC as Undermine I'd much rather run Hinder or Spell Crumple. Tucking a commander is much more valuable than doing three damage. I'd replace Remand with one of those two as well.

Proteus Staff maybe? I'd useful for tucking commanders, and given how few creatures you're running it can recycle a used-up Snapcaster or Venser into something else (that you then cycle back to Venser or Snap again next turn).

Exotic Orchard is a great card in a three-color deck.

Get at least a Strip Mine in there or a Maze of Ith or token deck running Gaea's Cradle is going to present issues.

Very cool. In a more competitive environment Wrexial is probably going to be significantly better at the same theme, but Sol'kanar sure gets style points.

Mudslide is guaranteed to eff over at least one other person.

The damage on Smash to Smithereens is nice but I myself would much rather have the option to hit multiple things with one spell either with Shattering Spree or an overloaded Vandalblast.

4x Darksteel Citadel? Makes a solid Ensoul target.

Generator Servant works great for rushing Scuttling Doom Engine into play (of which I'd have four)

Wirewood Lodge would be really useful here.

The Vivids come into play tapped, so if you're running come-into-play-tapped lands why not just run Golgari Guildgate or Gilt-Leaf Palace that at will still give you both colors all game. Tainted Woods, Woodland Cemetary, Twilight Mire and Llanowar Wastes are also options, and Urborg Tomb of Yawgmoth is great mana fixing. You could probably run a few less lands, too since it's a two-color deck.

I'd much rather pay one more mana on a Putrefy over Doom Blade and not only be able to kill black creatures but have the option to hit artifacts.

The biggest problem I had when I ran Oran was it just never seemed available. I always needed the mana and couldn't afford the luxury of paying one more to add a counter.

Okina, Temple to the Grandfathers maybe? Unless your meta runs a lot of Blood Moons or Back to Basics there really isn't much downside. I can't think of the last time I've had the luxury of using it, either, but at least it doesn't come into play tapped so even if I never use it I'm not out much.

Alchemist's Refuge has served me well as well.

While land thinning is indeed a thing, IMO people tend to way overvalue it in EDH because they think in terms of how huge it is in a 40 or 60 card deck vs. a 100 card format. It's one thing if you're running a handful of fetches so you take no hit while thinning your deck down by a considerable margin over the course of a game, but thinning it by one or two cards at the cost of a tempo hit is almost meaningless.

YMMV there, but I can say with certainty I've never thought "man, I'm glad I used that Terramorphic Expanse so I now have a 1.73% better chance to top-deck a non-land!" where as plenty of times I've thought "thank Erebos this land isn't coming into play tapped."

Since you're only running a couple of creatures consider Proteus Staff. In addition to being useable as a way to tuck enemy generals, it also lets you turn a drake into one of your amazing creatures. I run it in my Talrand along with just a couple of back-breaking creatures (Jin-Gitaxis, Stormtide Leviathan, etc).

In mono-blue decks Quicksilver Fountain can absolutely end people if it comes out early. Back to Basics can cause headaches as well.

Cards imprinted onto Isochron Scepter will trigger Talrand when cast.

Switcheroo is great here, too. "I'll trade a 2/2 drake for your general. Oh, and casting it makes me a drake."

Sapphire Medallion, Caged Sun and Extraplanar Lens make really good ramp in Talrand as well

In a three color deck Exotic Orchard is probably going to get you at least 2 of your 3 colors without the tempo hit from Evolving Wilds or Terramorphic Expanse.

Since you seem to be building a deck heavy on friend-alienating plays, I say go balls out and replace Counterspell or Syncopate with Spell Crumple.

Not sure it fits your deck but Dismiss into Dream is amazing in Derevi.

Molimo, Maro-Sorcerer is in the list twice.

Given how many fatties you're running Triumph of Ferocity might be a nice way to get an extra card each turn.

Rowen will get you a free draw about half the time, more if you're stacking your draw with Sylvan Library.

Extra-planar Lens would be a nice doubler.

I have a friend running a somewhat similar Nylea deck and Primal Order absolutely kills people.

One thing to watch; if people are killing your Planar Portal before you can use it three times (and I bet they are) then Ring of Three Wishes would be better as it's cheaper to cast and cheaper to activate.

Deadbridge Chant would fit a dredge deck pretty well.

Balance is banned in Commander.

Dolmen Gate really works great in Kaalia because it lets you attack into otherwise suicidal situations just to proc a demon/dragon/angel without worry of Kaalia (or your critter) dying. Knowing you can attack every single turn is pretty good. Alternatively you can use Reconnaissance to procc the creature and back them both out.

Linvala would fit well in this deck. Or any deck I guess, because there's no situation where saying "haha, your Ghave/Prosh/Rhys the Redeemed can't do anything" isn't useful.

Mudslide was amazing in my Kaalia deck, but I ran zero non-flyers. Even with the few ground guys you run it could still totally shut some decks down.

IMO Chromatic Lantern is a must-run in three colored decks. The fixing is just too good. I'd run it over the Talisman of Indulgence.

In any multi-player game Exotic Orchard is probably going to get you at least two of your colors, if not all three. I'd much rather run that than something as tempo-smashing as Evolving Wilds. Urborg Tomb of Yawgmoth is great fixing, too, and I'd slot that over Terramorphic Expanse.

If you're playing to win here, and I assume you are as this is a seven hundred dollar deck, then IMO you need a Maze of Ith, Strip Mine (for other Maze of Ith/Gaea's Cradle/) and Homeward Path (because getting Avacyn stolen SUCKS).