In addition to free drafting the Saviors Beta on Magic Online provided me with the cards to play around with a few constructed formats. I was never able to really make anything tournament worthy in Standard or Online Extended but I did manage to make a pretty decent Block Constructed deck.

Land:

1 Shizo, Death's Storehouse
Seven of the 12 creatures in this deck are legendary (counting the Genju). Nothing like giving a 5/5 fear without a drawback.

1 Miren, the Moaning Well
This was a late addition. I figured with 24 lands that make black mana I had the space for some utility lands. After looking at all of the lands in the block this was the only one that looked like it did anything worth caring about. I haven't actually needed to use the ability but it has never been a problem either and sacking Kokusho, the Evening Star to this sounds fun.

23 Swamp
This should be obvious. One thing of note is that there isn't any decent mana acceleration outside of green in Kamigawa Block. This deck would love cards like Solemn Simulacrum, Guardian Idol, and Wayfarer's Bauble but unless you want to use Honor-Worn Shaku there isn't anything but land. Being a control deck this deck needs a lot of land so I went with 25.

Creatures:

4 Hand of Cruelty
This was originally Takenuma Bleeder. The Bleeder was actually pretty good against control but the life loss sucked against WW. The deck wasn't doing as well against WW as I thought it should so I threw this in to make that matchup better. It was not only better against WW but was also better against burn decks and wasn't really any worse against control. It does become crappy once you drop Night of Souls' Betrayal though. This usually gets in 3-4 attacks against control decks and is a great blocker against aggro. It buys you the time you need to drop Night of Souls' Betrayal.

3 Yukora, the Prisoner
One of the two finishers in the deck. This guy is cheap enough that he come out early to also hold off smaller creatures from aggro decks.

4 Kokusho, the Evening Star
This is the big finisher. While not stupid like it is in multiplayer it is still the best black creature in the block. This won me more games by being a 5/5 flyer than its ability so only drop that second one if it will kill your opponent.

Spells:

4 Distress
I wish there was more good cheap discard in the block but this is really all there is. It has been pretty helpful though. Without this the control matchps would be a lot harder than they already are.

4 Cranial Extraction
Honestly this card is a tiny bit overrated. That doesn't mean is isn't great though. Just not broken like many other people call it. While it rarely ever will shut down an entire deck it can remove troublesome cards. Also casting this after a Distress can let you treat it like a Cabal Therapy. One of the best things this card does is just remove opposing copies of Cranial Extraction. Against green I like to try to get rid of Kodama of the North Tree since this deck has trouble dealing with him.

4 Sickening Shoal
This has been quite amazing. It lets you kill things while tapped out. I've hard cast it just as often as used the alternate cost. It doesn't even care about silly things like being Indestructible. After using it I'd would have to say it is the best Shoal (AKA better than Shining Shoal). It also gives you something to do with those extra copies of Night of Souls' Betrayal you drew.

1 Genju of the Fens
I randomly threw this in as a one-of at one point and it proved itself to be worth the slot. While not amazing it was generally a nice way to get damage in in the late game. It was also good as a potential blocker against aggro and often held a few creatures off. I doubt it would be worth adding an extra copies though.

4 Pithing Needle
This is another card that has been amazing. I always want to see 1-2 of these during a game. I can't tell you how many times I've shut down Umezawa's Jitte or Sensei's Divining Top with this.

4 Night of Souls' Betrayal
This is the key card in the deck. It makes aggro decks a lot less scary and turns cards like Hana Kami, Sakura-Tribe Elder, Nezumi Shortfang, and Sosuke's Summons into dead cards. This is the card that makes this deck not suck.

3 Hero's Demise
This was originally Horobi's Whisper. I had these in the sideboard instead. Eventually I tried them out maindeck and they were amazing. Every single deck in the environment seems to be running huge amounts of legendary creatures. Not are all the most threatening creatures legendary but most of the creatures this doesn't kill have one toughness and thus are shut down by Night of Souls' Betrayal. I have not played a single game where I wished this was a different removal spell. Between this and Night of Souls' Betrayal the only creature that is hard to deal with is Kodama of the North Tree.

Sideboard:

4 Hideous Laughter
This was originally in the main deck but ended up not doing much except in the WW matchup. Even there it rarely killed more than 1-2 creatures at a time. It was just inferior to Night of Souls' Betrayal in every way possible.

1 Hero's Demise
There are matchups where the 4th copy is nice to have.

2 Eradicate
This is mainly to bring in against decks running the dragons. I haven't actually used this yet so it likely isn't a good choice for the slot.

4 Nezumi Shortfang
This is brought in against control decks that don't care about Night of Souls' Betrayal. The two cards have bad synergy so running both isn't usually a good idea.

4 Kiku's Shadow
This is for decks that don't run many legends or against an aggro deck that you need more removal to beat. They kill most things you need to kill in block with Meloku the Clouded Mirror being a notable exception.

I haven't played many full matches so I'm not entirely sure about the sideboard. I'd say there are a couple cards that would be better as something else.

Cards to think about:

Nezumi Graverobber
Old versions of the deck has this in the sideboard but got removed for Hideous Laughter once I decided that shouldn't be in the main deck. It is good against decks like Legends.dec and Gifts Ungiven but not really amazing either. This may still belong in the sideboard.

Ink-Eyes, Servant of Oni
This is good but a bit expensive when you can't ninjutsu it out. I think Yukora, the Prisoner is a bit better in this deck. Then again maybe dropping a Kokusho, the Evening Star and a Yukora, the Prisoner for two of him might make the deck better against Cranial Extraction. He is the best creature to give fear with Shizo, Death's Storehouse.

Kagemaro, First to Suffer
I never gave him much of a try but given the number of cards usually in your hand he would usually be a 4/4 which isn't that good. If there was some type of good black card drawing in the block he would likely be much better.

Kuon, Ogre Ascendant
I had this in the deck at first as well but eventually removed it. First you will pretty much never flip it. I player like 15 games before removing and I never flipped it. Not even once. That was with 4 Night of Souls' Betrayal and 4 Hideous Laughter in the maindeck. Not even WW was put into a position where this could be easily flipped. Even if you do flip it what then? Since there is no Drain Life in block you pretty much have to rely on Genju and Kokusho, the Evening Star triggers to win which means probably not at all. This is basically just a 2/4 for 3 mana which is still not too bad but Hand of Cruelty performed much better here. As cool as it looked at first glance Kuon is unfortunately a bad card.

Seizan, Perverter of Truth
This is pretty much the only card drawing effect available in in black for the block. Unfortunately it sucks balls. Casting this against aggro will help them kill you. Casting it against control will give them the cards they need to kill you. Don't play with this piece of crap.

Journeyer's Kite
This was slow. Not just a little slow but so slow that it was terrible. You will practically never have the spare mana to activate this until you have already dropped your fatty and are trying to win. At that point you don't need more land.

Sensei's Divining Top
This card is amazing in other decks but not here. This deck does not contain a single shuffle effect and thus you will see the same 2 cards clogging up the top of your library every turn. Without shuffle effects the Top doesn't really do anything. Besides if I ran it Pithing Needle could not longer shut it down without creating dead cards.

Matchups:

Gifts:

This is the general consensus best deck in block. That said it is a pretty decent matchup. Often it is just a resource war. If you can Cranial Extraction for Gifts Ungiven before they can cast it they will be slowed down a bit. After that choosing targets is a bit harder since they basically just run a few copies of a bunch of different things (since that is how to break Gifts Ungiven). You may want to Extract their Cranial Extractions even though they only have two because it does more damage to you than to them. Hero's Demise is great here as it kills everything but Kodama of the North Tree if they run it. I've had games where they ended up going through every single creature in their deck and still won. The Hana Kami + Soulless Revival combo isn't a problem as you have 8 maindecked cards that shut it down (Night of Souls' Betrayal and Pithing Needle) and most only run one Wear Away (though a couple run 2 copies). As for boarding I think pulling Night of Souls' Betrayal for Nezumi Graverobber and finding space for the 4th Hero's Demise is the right call. This isn't an easy matchup but certainly isn't bad either. It put it in your favor though.

Snakes:

This isn't a bad matchup at all. Night of Souls' Betrayal shuts down their smaller snakes so you just have to use Hero's Demise and Sickening Shoal to keep the legendary snakes off the table. Some decks run Kodama of the North Tree which is much harder to deal with. The most common way of killing it is to trade Yukora, the Prisoner with it in combat. If you know they are running it try and get rid of it with Cranial Extraction. Most don't run any and I've never seen a Snake deck run more than one but it is the card you least want to see. For boarding you want your 4th Hero's Demise and swapping Cranial Extraction for Hideous Laughter might be a good ideal as well. This is actually a pretty easy matchup.

Legends.dec:

This is another easy matchup and I don't even think it is a very good deck. It is basically just the Gifts Ungiven deck without Gifts Ungiven which was the best card in the deck anyway. While this deck was popular before Pro Tour Philly it was basically replaced by the Gifts deck. I wouldn't expect to actually see any of these. Treat it like Gifts without Gifts and it'll be pretty easy.

White Weenie:

This isn't too bad unless they get a great draw or you don't draw removal. Hand of Cruelty is great at holding them off long enough to drop Night of Souls' Betrayal which shuts down a third of their deck. Try to drop a Pithing Needle for Umezawa's Jitte or take them out with Cranial Extraction or you will have problems. If you can get out Night of Souls' Betrayal and eliminate Umezawa's Jitte you should be able to win. If you can't you probably wont win. Be careful of Hokori, Dust Drinker. It can cause a few problems. Try to get rid of it with Cranial Extraction. It isn't game over though as Sickening Shoal can still deal with it when your lands are all tapped. For boarding you want to pull Cranial Extraction for Hideous Laughter and Distress for Kiku's Shadow. After this beating them should be easy. You may want to leave in something like 2 Cranial Extraction for Umezawa's Jitte and Hokori, Dust Drinker (Probably by only bringing in 2 Kiku's Shadows.).

Burn:

This is your bad matchup. Were cards like Mind Sludge, Persecute, and Consume Spirit in Kamigawa Block this would likely be a different story but as it is you are in for an uphill battle. The goal here is to get a fatty in play a quickly as possible and try to race the burn. Unfortunately this is easier said than done. If you can knock burn spells out of their hand with Distress and Cranial Extraction you stand a much better chance. About 90% of these decks run Hidetsugu's Second Rite so don't let it surprise you and don't be at 10 life. Getting rid of it with Cranial Extraction might not be a bad idea either. There isn't anything amazing in the board for them and if this deck becomes popular that should likely change but at the very least you can pull the dead Hero's Demise for something at least a little useful. Nezumi Shortfang is likely the best choice at either that will get in a few activations and get rid of some burn or make them use a spell to kill it and thus get rid of some burn.

Heartbeat of Spring:

These decks are fun but not all that good. You want to Cranial Extraction for Heartbeat of Spring to slow them down a lot. This makes the rest of the deck much more manageable. Without the Heartbeats this is basically just a bad Gifts Ungiven deck. If they get a Heartbeat of Spring into play however you probably just lost. You just can't keep up with that much mana and can't abuse it like they can. If only Consume Spirit were legal.

Conclusion:

This deck is actually quite good and is likely one of the better decks in block. I doubt this is the optimal build but it is certainly a good start.

This may be a good deck for block but I don't think MBC will be a tier 1 Standard deck. It has a lot of powerful tools and access to card drawing like Night's Whisper and Phyrexian Arena will make Kagemaro, First to Suffer worth using if not very powerful. The problem lies in the fact that this deck would have trouble stopping Tooth. Discard is pretty good against Tooth but Sensei's Divining Top makes it easy for them to win off the top of their deck. If you can design a version of MBC with a good matchup with Tooth it can certainly be one of the better decks out there but until then it will likely be a tier 2-3 deck. I fully expect it to take a few slots in top 8s of Regionals but top 8ing Regionals does not make for a tier 1 deck. Regionals is almost known as the land of the rogue decks.