While this card isn't amazing, I think most people are overlooking the fact that the randomness cuts both ways in this case. Your opponent gets to see what all 3 cards are, but not which one makes it into your hand. That can be very important when working with bloodrush cards.
Night Terrors isn't bad. I can see myself drafting it in Limited. Desperate Ravings too, since it's instant speed, especially if I've got a flashback heavy deck that doesn't mind a bit of self-discarding.
Ranger's Guile = I usually enjoy playing the little instant green pump spells that every set has, but I doubt I'll ever be using this one much.
As far as good Red cards go, I think people may be underestimating Act of Aggression. A 5 mana Threaten doesn't seem good at first glance, but the instant speed adds some new possibilities. Stealing one of your opponent's attackers to use as a blocker is often going to result in a 2-for-1, which isn't bad for 3 and 4 life. Probably not strong enough for Constructed, but I'm going to love them in Limited.
I wish they'd focused a bit more on stealing creatures/permanents, which is one of the abilities the two colors share. The only UR card I can think of that does that is Dominus of Fealty. I'd love to see a card like
Threaten, Izzet Style UR
Instant
Gain control of target permanent until end of turn.
I liked the review, but I have to disagree with his assessment of Tainted Sigil as unplayable. Its worth isn't in using it as a pseudo-fog, it's using it to cheat the cost of cards like Ad Nauseam or Phyrexian Processor.
I was thinking of making a deck like this. He also works well with other creatures that are forced to leave play at end of turn, like Incandescent Soulstoke or Impromptu Raid.
The one redeeming aspect to this guy is that his unearth ability works well with Glassdust Hulk and anything else that cares about artifacts coming into or leaving play.
Reminds me of Snakeform, which I love. Another 3 CMC GU pseudo-removal card. It doesn't have the cantrip effect, but it can kill shroud, so I'm happy with it.
The wording on Aven Mimic is very interesting. "At the beginning of your upkeep, target 1 creature. You may put a wing counter on that creature. If you do, as long as the creature has a wing counter, it is a 3/1 with flying." It may just be a difference in the way the Japanese cards are formatted, but as written you can target a creature without actually putting a wing counter on it, which could be used to trigger any "when this creature becomes the target of a spell or ability" effects.
Also, I can confirm that the text on Tar Shards tells you to put the cards on the bottom of your library in random order. It also looks like a triggered ability, since the text definitely says "when you play this spell, ...".
I wouldn't be surprised to see something like this:
New RG Land
Land - Mountain Forest
When this comes into play, return a Mountain or Forest you control to your hand. (If you control no other Mountains or Forests, you must return New RG Land to your hand)
:symtap:: Add or to your mana pool.
It points out to new players that the lands also have the basic land types, and helps encourage good play when they figure out that they can tap the Mountain or Forest they're returning for mana before they play this.
According to the Orb, 'exalted' shows up 12 times and 'alone' shows up 15, so it looks like there will be 3 cards that give an additional boost to creatures attacking alone. I'm guessing it'll be a 3-color cycle: a white creature that gives lifelink (Battlegrace Angel), a blue creature that gives flying, and a green creature that gives trample.
Ranger's Guile =
Threaten, Izzet Style
UR
Instant
Gain control of target permanent until end of turn.
I was thinking of making a deck like this. He also works well with other creatures that are forced to leave play at end of turn, like Incandescent Soulstoke or Impromptu Raid.
Also, I can confirm that the text on Tar Shards tells you to put the cards on the bottom of your library in random order. It also looks like a triggered ability, since the text definitely says "when you play this spell, ...".
New RG Land
Land - Mountain Forest
When this comes into play, return a Mountain or Forest you control to your hand. (If you control no other Mountains or Forests, you must return New RG Land to your hand)
:symtap:: Add
It points out to new players that the lands also have the basic land types, and helps encourage good play when they figure out that they can tap the Mountain or Forest they're returning for mana before they play this.