Languish: this card is getting hyped by the sites with writers who sell cards. It reminds me of Collected Company. It will be good in Standard, it will help the secondary market, and once it cycles out of Standard we will never hear of it again.
Erebos's Titan: I want this card bad. It has a home in a Devotion to Black deck in Standard. I am not sure if it is good enough to make Devotion to Black a good Modern deck... that sounds like a stretch. Still, its a 4 drop 5/5 without a drawback, and that reads at least rare, fair for Mythic. It is not Legendary: great!
Demonic Pact: You can only play this card when you are certain the game is yours with it, otherwise, it will lose you the game, which is fair for a 'Pact' card. Its a 4 drop, and that means it will see some fringe Standard play. I don't see it in Modern.
Despoiler of Souls: If it had Haste it would be really something. Without Haste, it will sit for a whole turn after you reanimate it.
Graveblade Marauder: Nice! And its a 3 drop. I want to combo this critter so bad! It has great stats: survives Lightning Bolt, can chump block and live with Deathtouch, and with a graveyard full of critters can win you a game here and there.
Infinite Obliteration: a casual Surgical Extraction (which can be cast for two life and no mana-Phyrexian mana is sooo broken!), great for Standard. I am guessing that Wizards is worried about a specific card that could break the Standard format, and this card is here to make sure that doesn't happen.
Kothophed, Soul Hoarder: its Legendary, but who needs two on the battlefield? In Modern casual with a board wipe this card can draw you a slew of cards. In Standard there's Crux of Fate. It requires a lot of mana to make for a big effect, yet sounds like a lot of fun.
Tainted Remedy: a 3 drop? Wow, this is awesome. Now I need to go on a hunt for all the cards in Modern that can give your opponent life. In Standard there won't be as many that are aggressively costed. I want this card bad.
Priest of the Blood Rite: its not Legendary and it will hit for 7 if it and its token are not blocked. That can be good to great, at least in Standard. I would flicker it in Modern in white black using Restoration Angel and/or Cloudshift. There are many references to Avacyn Restored in this set!
Abbot of Keral Keep: with a lot of Scry this card could be really useful. Its a two-drop, and that makes it very playable. I can even see it in Red Deck Wins (RDW). But you can only use the effect as an Enters the Battlefield (ETB) effect, and that means you get it once unless you flicker it.
Chandra's Ignition: useful board wipe in battlecruiser Standard. But... if you have the biggest creature on the board you are already ahead... I need to think about this one. The 'each opponent' part can win games. It reads like a Commander card, and can do great in Standard constructed.
Avaricious Dragon: great Dragon, should have been in Dragons of Tarkir (there is a set that needs more playable dragons, and I am not kidding, so many unplayable crap dragons in that set). In Modern I would play it with Hellrider and a bunch of goblin tokens generated by Krenko. In such a deck you play with an empty hand anyways. By the time you cast this everything in the deck can be cast when drawn.
Embermaw Hellion: an additional hit for one is not great if you have two or three critters, but if you have six or seven goblin tokens on the field, this effect can win games. In Modern, there are many cards that hit the player for 1 or 2 under various conditions. Take Underworld Dreams (a 3 drop black enchantment that reads "Whenever an opponent draws a card, Underworld Dreams deals 1 damage to him or her.") We are talking casual Modern or Commander, of course.
Flameshadow Conjuring: as a 4 drop it will help in Standard constructed, not sure for Modern. Its only one red mana to get a copy of what you just cast. This is a very useful card, I want to play it.
Goblin Piledriver: old school reprint. Dies to Lightning Bolt, but if it doesn't die, with a bunch of goblin tokens on your side of the field you can cause some serious damage. I am not seeing enough goblins in standard, though. Maybe there will be lots of goblins in the next block. There are 14 now, but some are really heavy or not in red.
Molten Vortex: a remake of an old classic, Seismic Assault, which for three red mana can get you this effect at no cost. This one comes in earlier but is not free. Still, a great remake. I want to play this card in Standard, but I need a way to have a hand full of lands.
Scab-Clan Berserker: great as a sideboard card against blue decks. Otherwise, if your opponent is not casting noncreature spells this card is a 3 drop 2/2 with haste that can become a 3/3.