Hey there! Sorry for the delay. I looked through a ton of black cards, and then have done a bit of playtesting myself. Below is the list I have been refining towards all night.

I agree with your assessment of Bloodline Keeper — awesome card! but not as good in this deck.

In my playtests, I found that I actually didn't need very much card draw. The Priest gave me a little, which was enough. So I completely removed Mask of Memory for more synergistic effects.

This list generally "goes off" turn 6 - 8 and wins straight away.

Decklist

Creature (16)

4x Blood Artist
3x Geralf's Messenger
4x Priest of Forgotten Gods
3x Qarsi Sadist
2x Undercity Informer

Enchantment (11)

4x Bitterblossom
4x Bloodchief Ascension
3x Grave Pact

Sorcery (9)

4x Beseech the Queen
4x Collective Brutality
1x Torment of Hailfire

Land (24)

24x Swamp

Maybeboard

Ruthless Ripper
Syphon Life
Smothering Abomination

Card analysis

Torment of Hailfire is an amazing finisher if you have lots of mana but are stalled out otherwise. You don't want more than 1x of it, especially since you can tutor for it if need be.

Collective Brutality proved to be one of the best additions to the deck. Early on, you can activate its third mode to help get Ascension counters. Once Ascension is activated, then its discard mode gets the Ascension trigger. It also can kill a creature, triggering all of your death synergy. It's just so flexible!

I cut Grave Pact down to 3 copies, just because it has a higher CMC and you really don't need more than 1 in play (maybe 2 if going against a deck that "goes wide"). Considering you have 4 tutors, this means you basically have 7 copies of it, so you're nearly guaranteed to be able to get it.

I like the addition of Undercity Informer , but he has no stacking effect and doesn't have to tap, so having more than one in play isn't helpful. He also feels like a mid- to late-game play, when you have the extra mana and creatures to sac them all and finish off an opponent.

Geralf's Messenger did some major work in this deck. Absolutely loved getting him. I considered even upping him to 4x. I'm not as in love with Qarsi Sadist , but I was also never disappointed to draw him, as the Exploit sac outlet provided another means to put a counter on Ascension, as well as trigger any Artists or Grave Pacts I may have in play.

Maybeboard thoughts

I was looking at Ruthless Ripper because I think it's very important to get Ascension online as quickly as possible, which means being able to make the opponent lose 2+ life during his turn, not just during yours. Currently, the only instant-speed option is Priest of Forgotten Gods (or an Undercity Informer if you have a Geralf's Messenger with no counter on it or 2+ Artists out). The Ripper provides another instant-speed option that doesn't rely on having another card out. But other than that, there's not any other synergy with the deck. I haven't playtested it, though.

I was considering Syphon Life just for its Retrace ability, which can help in mana flood situations, late game if things are stalling, etc. I haven't playtested it, but again, other than its repeatability (which gives you card advantage), it doesn't do multiple things like Collective Brutality or Qarsi Sadist does.

I would try out a 1x of Smothering Abomination just to give the deck reach if the game goes long. I like the idea of card draw that doesn't drain you life. Since many of your creature deaths will be due to sacrifice, it's almost as effective as Dark Prophecy . And while it costs 1 mana more, it also gives you another creature. Even its downside of forced sacrifice isn't that bad, since you can turn it off at any time by sac-ing itself to its own ability.

One more thing I forgot to comment on — I saw your comment regarding the Modern Storm deck you faced. Sadly, that seems to be how Modern is in general these days. Many of the decks try to win by turn 4, and crazy combos like that aren't uncommon. It's one of the reasons I've backed off from Modern recently, as I prefer a less degenerate format!

So while I love your deck idea, I'm not sure how viable it'll be in the Modern format, at least in truly competitive environments. That said, I wish you all the best in finding a way to optimize it down to a turn 4-5 win!

On the subject of winning games with my deck, trying to win early is one approach, but another is having cards that stall out or shut down opponents, making it harder for them to play.

In some ways, the deck already does some of this with the oppressive sacrifice mechanics, making it very hard for opponents to keep creatures on the board. My hope is that I can disrupt opponents in other ways which will give my deck time to get moving.

I liked your analysis of the deck list you provided. I've always had an issue taking anything but 4 of a card (probably my OCD) but you make a good case for why that isn't always optimal.

One thing I would be interested in doing to accelerate the deck is getting creatures with enters the battlefield or leaves the battlefield effects to trigger multiple times, whether this means copying the creatures, finding ways to duplicate the effects, or resummoning/flickering the creatures. Something like this could be amazing with a card like Qarsi Sadist . Can you think of any way in which I could reliably accomplish this?

On a possibly related note, the reason why I enjoy heavy card draw is because it lets me throw more things at the opponent (enchantments, creatures, etc.) - Essentially putting more shots downrange, which couples well with the deck's low mana curve. I'm planning to test this and see if it proves effective in speeding up the deck's march to victory. It might be helpful for fighting control decks as well. If I throw enough cards down, they'll be hard-pressed to counter them all.

I agree that control via stall tactics is a viable strategy, but the problem I foresee is that the "sac oppression" doesn't actually start until Grave Pact is out on turn 4. For most Modern games, that's simply too late. (For instance, I have a Co-Co Elves deck that was reliably Overrunning you with elves on turn 4-5 for the win.) If you had cheaper forced sacrifice to stall until Grave Pact came online, it might work.... but I'm still not sure.

Then again, it's been a couple years since I've played in the Modern format, so I have no idea what the current meta is like. Maybe a few more games on Cockatrice will give you more data!

As to abusing ETB/LTB effects, I'd have to do some searching, but off the top of my head, copy effects are usually in blue while flickering creatures are usually in blue/white. Resummoning (or more commonly known as reanimating) creatures is definitely in black, but a lot of the best ones aren't Modern-legal — you'd have to dip into legacy. All the Modern options have a very high CMC.

Your best bet is probably copying the triggers. For that, you have two options — Panharmonicon and Strionic Resonator . The former only copies ETB triggers, so you'd want to build your deck to focus on that, but it'll give you double Exploit when Qarsi Sadist ETBs (note it will NOT double up his second ability) and Geralf's Messenger will drain for 4 instead of 2.

I personally feel that the Resonator will probably be better. It hits the table earlier, and although it requires mana to activate, this actually has great synergy with Priest of Forgotten Gods , who gives you the 2 mana you need. In fact, SO many times in playtesting, I used her ability during the opponent's turn but sadly didn't have any instant-speed ways to take advantage of the mana I got. Now, however, even if you're tapped out, you can activate her*, and then any abilities that your opponent's sacrificed creature triggers (Bloodchief Ascension, Blood Artist, Grave Pact) can be copied with the two black mana. And obviously, any other trigger can be copied — double tokens from Bitterblossom, double Exploit as described above, double drain from a single Exploit with the Sadist or from the Messenger's ETB, etc.

* Note that any triggers caused by the two creatures you sac for the activation cost will resolve prior to you receiving the two black mana, so you can't use the Resonator on those triggers unless you have other mana open.

The question is, what would you take out? I still believe that 4x Grave Pact is too many. I'd personally cut that down to 2x and add 2x of the Resonator. Since you have such a low curve, you might be able to get away with 23 lands (much like low-curve red decks can; some even run 22). Then you could bump that up to 3x.

This may sound crazy, but what if I dropped Bloodchief Ascension entirely? In my experience, I can get Grave Pact out before I can reliably stack my Bloodchief Ascension . Sure, it's amazing if I can get it stacked, but if I don't have to worry about that, I can focus on using cards like Blood Artist and Zulaport Cutthroat , which have similar effects that start working as soon as I put them on the field. If run both those cards, a single creature dying could trigger some explosive effects which could drain enough life to keep me alive long enough to get that Grave Pact out in the first place. In this situation, I could still deal with creatureless decks by killing my own creatures over and over, triggering every Blood Artist and Zulaport Cutthroat I had on the field. The only disadvantage to this is that I would have no 1-drops, but if my only 1-drop isn't proving reliable, I see no reason to keep it around in the first place.

On that subject, how consistently have you been able to stack Bloodchief Ascension vs. getting Grave Pact out? Have you found any mechanical tricks or favorite combos that have helped you along the way?

I love the idea of Strionic Resonator and seeing how many things it can interact with (practically my whole deck)! It really does seem like a perfect fit. I plan to do some testing with that as well and see if my deck is or isn't slowed down by the removal of a couple copies of Grave Pact . With the change I mentioned above, I may be able to stay alive long enough to pull one out via Beseech the Queen , so it might be okay.

After a few additional games which include me losing a game on turn 2, I have concluded that Manamorphose should be banned in modern.

It's getting to the point where if you don't pull an insane combo by turn 2 or 3, your opponent probably will. It's exactly the problem you see in vintage and legacy, and now it's crept into modern. It eliminates a huge number of strategies from being viable. Either you play storm or you lose. All I want to do is play the game without being forced to use one or two specific strategies. Whatever happened to creativity and having options in deck building?

You know what? No! I don't think you're crazy. After a few more playtests, I agree with your hunch about Ascension .

I mean, it's not a bad route (at least, not in a less fast-paced format than Modern). Assuming it was in my opening hand or I could fetch it turn 3 with Beseech , I was able to reliably get it activated by turn 5-6. Between Geralf's Messenger , the Priest , Qarsi Sadist , and Collective Brutality , I never had issue draining life.

That said, it does take a bit of work. Also consider that by the time you've activated it, you've drained nearly half the opponent's life (assuming no lifegain; if you face lifegain, this card might help catch up to them). This is an amazing card in slower formats like Commander, but definitely isn't suited to Modern.

Speaking of....

I couldn't help but chuckle at your most recent comment of frustration. You're expressing the exact reason that I got tired of Modern! I'm with you — I like creative deck building and formats that give each deck a chance to show off what it was designed to do. Modern isn't that anymore.

Anyways, yeah, you could try cutting the Ascension and perhaps shave off a couple copies of some of the other cards in order to fit in Zulaport Cutthroat and Bloodghast .

Oh, so I remembered you mentioning that mill worried you, which was one of the reasons you wanted to keep Elixir of Immortality . I forgot to suggest that you sideboard a single copy of one of the original Eldrazi titans from Rise of the Eldrazi — Emrakul, the Aeons Torn , Ulamog, the Infinite Gyre , or Kozilek, Butcher of Truth . Some people also recommend adding 2 copies, since there's always the risk of drawing it. But yeah, basic idea is a solid anti-mill tactic. :)