Having no hand size is fine with Ghirapur Orrery and Asylum Visitor drawing you cards when you're Hellbent (no cards in hand). If you play it right, you can actually create a decent amount of card advantage for yourself.
Before we go any further, let's take a look at the deck list:
4 Falkenrath Gorger
4 Asylum Visitor
4 Furyblade Vampire
2 Bloodhall Priest
Non-Creature Spells (22)
3 Avacyn's Judgment
3 Cathartic Reunion
3 Harnessed Lightning
3 Key to the City
4 Fiery Temper
2 Ghirapur Orrery
2 Midnight Oil
2 Murderous Compulsion
4 Foreboding Ruins
4 Smoldering Marsh
Asylum Visitor is only 1B and she's a 3/1 that can draw you a card when you have no cards in hand. You only have to pay 1 life for this, too. Believe me, she will draw you cards. Considering how aggressive she is helps, too.
There are only 2 copies of Bloodhall Priest in the deck because running more ended up clogging up my hand in playtesting. Two copies are enough because the true value of the Priest is when you have no cards in hand. A 4/4 for 4 is OK, but her Madness cost is only 3 mana. Then, if she enters the battlefield or attacks when you have no cards in hand, she deals 2 damage to a target creature or player. This effect has won me games by itself. You would think more would be better, but really, you end up just getting a 4/4 for 3 most of the time. While this is good, you're trying to move so fast that sometimes you need another spell instead of her.
Cathartic Reunion both enables Madness and nets you 3 cards. The full four copies were too much. At times, you even end up discarding your third copy, but it's a great card.
Harnessed Lightning isn't a Madness spell, but it's just too good to not play three of. The energy does make a difference, too, as you play more in a game. And it's instant speed removal!
The last Madness spell in the deck are 2 copies of Murderous Compulsion. I'm thinking these should just be Unlicensed Disintegration. While Compulsion is a Sorcery, if you happen to discard it for Madness, you get to play it at instant speed. However, Unlicensed Disintegration is probably better overall, so I may switch these two spots to that card. As I build a sideboard, I may shift these in there to combat more aggressive decks in which Midnight Oil really doesn't help me.
But wait, there is another drawback! Whenever you discard a card, you lose 1 life. This is kind of bad, but it can be fine if you're going to win the game anyway. But you can see why we only want 2 copies. You also don't want to be drawing all these cards, because you can actually kill yourself with these triggers (although it only happened to me once).
Also, extra copies of Midnight Oil can be dead in your hand and cost you the game by not being another spell that you need instead. Being four mana means that you won't always want or need to cast it. The good news is, that you actually don't mind discarding to hand size if you have the mana to cast your Madness spells. Also, there are some other synergies with other cards as you'll see in a moment.
Do keep in mind that you want the Orrery trigger to activate instead of your Asylum Visitor's, if that's the case. Again, you only want two of these, because they are 4 drops in an aggressive deck. Plus, you don't really need more.
Then there's Key to the City. This card a great Madness enabler and a great way to consistently push through 3 or 4 damage that can't be blocked. Also, whenever it becomes untapped, it can draw you a card. If you stack your triggers correctly, you get 4 cards off of Orrery and the Key instead of just three. This card is really good, and you really don't mind having multiples. A fourth copy may end up coming in out of the sideboard. It's a good card in other decks, but in a Madness deck it's particularly powerful.
This deck seems pretty solid, but it hasn't been played against the Top 8 decks just yet. It really needs a sideboard, and as I said, Unlicensed Disintegration would definitely be in there. A fourth copy of Key to the City should be in there , too. Midnight Oil seems like it's a good card in the deck, but I wonder if it's even completely necessary to the deck's success. I'm not entirely sure just what to add otherwise and am very open to suggestions.
If anyone wants to give this deck a spin and finds that the list needs to be adjusted (the addition of Chandra, Torch of Defiance, perhaps?), please let me know what you've found! This deck is cool and while I'm not sure it's Tier 1, I think it's good enough for a Friday Night Magic run.