This plays like a combo deck.
*Seal of Fire, Sparkmage, Staggershock and Emberwilde Augur all serve as either removal or let me play Rakdos consistetly on turn 4. Late game they're useful as cost reducers for Bloodgift Demon, Inferno Titan and Maga, Traitor to Mortals.
*Inferno Titan is a good card. The burn is nice with Rakdos and he benefits from costing only :symr::symr:.
*Bloodgift Demon gives us card advantage so we don't lose steam, and if I want to I can target my opponent with his effect.
*Maga can be pretty devastating if she doesn't win the game outright; Turn 5 after swinging with Rakdos and hitting them with some "free" burn like Seal, rebounded Staggershock or Augur, she comes down as a fat body and causes massive life loss. Usually the finishing touch, but burn spells, Rakdos, Inferno and Bloodgift fill that role nicely too.
*Demonic Tutor is a fantastic card. It gets me what I need, when I need it. Improves my chances of hitting turn 4 Rakdos, or gets me a Maga to follow up with, etc.
*Blightning is essentially free hand disruption with a Rakdos out; it costs and deals 3 damage.
I've only played the deck once, but the list I have right now looks like it will struggle against aggro decks.
While it's a solid idea, the costs in this deck are outrageously high to the point that if your Rakdos is killed that you have no recourse. Augur of Skulls and Emberwild Augur don't necessarily make for a strong lead out the gate, where the most atypical of casual decks will drop a strong creature turns 1, 2 and 3. Even if you hit both an Augur of Skulls and a Blightning on a single opponent, none of those target so it's still viable that they'll either hold a removal spell to eliminate your key creature (which, when someone's forcing you to discard the best things to hide are either land or removal if you're playing aggro) or topdeck one if they're running the typical 4-8 kill spells.
For the most part, you have a lot of things that flat-out rely on getting Rakdos when you're going to go one out of every four or five games without even drawing him (including the 1 Demonic Tutor into the calculation, Bloodgift Demon turn 5 isn't enough to significantly change the numbers either), notwithstanding every good deck packs removal (4-8 spells) so killing Rakdos will most likely end in this deck stopping cold.
You should have maybe 8 cards at most that greatly benefit from Rakdos being out, not revolve a whole deck around a creature that gets ended by a kill spell and runs your deck into a wall. Opting to protect him as much as possible would dilute the hell out of the effectiveness of the deck (and still not stop removal entirely), and you're not running enough to removal to viably stop aggro in the event they do kill Rakdos, which they will if their deck is constructed decently.
I find Keldon Marauders as being perfect for this kind of thing: He's a 2 mana creature that can cause 5 overall damage on his own, and his vanishing ability is mana-less so if you cast him turn 2, by turn 4 he pings the opponent for 1 and it doesn't require you to play sub-par cards to allow yourself to cast Rakdos- You got a solid, powerful creature on turn 2 that can block for you, and still deals 2 damage even if he's blocked after you swing.
Rift Bolt is, in my opinion, a much better early game card than Staggershock. Sure, it's cute that you can retrace, but again, when your Rakdos is inevitably killed your deck becomes insanely mana hungry and tossing lands just isn't the right call. You can easily set up casting Rakdos with this card.
I have an idea that might be a bit more resilient, overall, if perhaps lacking that gigantic finishing punch from Maga (but at least you won't be rolling over and dying to literally every deck that runs 4 Swords to Plowshares and 3 Oblivion Rings). The bottom line is, I think Maga is clearly win-more. IE, you'd win the game anyway without her, but in a less-flashy fashion. If you can resolve a Seal of Fire, Rakdos, Bloodgift Demon, etc., to drop a big-ass Maga and deal a huge amount of damage to your opponent, then you were already going to win because your opponent already lost, at minimum, 15 life without turning a creature sideways before this combat step, meaning that her damage dealing capacity is moot if it only means you were going to win anyway.
Hymn to Tourach would probably be better use of Blightning's slot, and I added Vampire Nighthawk over Gatekeeper of Malakir because the Gatekeeper isn't evasive and BBB for a 2/2 plus an Edict is kind of hard in a two color deck.
Overall, being aggressive and attacking with evasive creatures is the easiest way to allow the casting of Rakdos, in my opinion. There are some cards I'm still forgetting that would probably make this run even smoother, but I'll edit later if I recall them.