As requested, here is the EDH list built around the all-knowing Seizan, Perverter of Truth. This is a "suicide black" deck, focused on:
[A] drawing the game out with black control
[B] grinding your opponents' life totals away incrementally
[C] flooding opponents' hands and forcing massive discard
[D] surviving Seizan's global bleed effect
[E] blending in to multi-player politics
Playing Seizan is all about timing, deception, and understanding the nuances and intricacies of your personal playgroup. When you pilot Seizan, you assume the role of puppet master in a drawn-out game of delicate misdirection and politics--vying not only for control, but for the power to allow someone else to think they're in control. Seizan doles favors, makes deals, signs contracts, and always collects payment. One way or another, every player owes Seizan in the end, even you.
The deck is comprised of 'rattlesnake' creatures to deter opponents from swinging at you early game; Typhoid Rats, Vampire Nighthawk, Wall of Souls, Wall of Shadows, Nirkana Cutthroat, etc. Deathtouch and rebounding damage can buy you time in the early game and allow you to get your tutors off and blend in to the realpolitik as it begins. The key to many multiplayer meta environments is to seem like as little of a threat as possible early on. Seizan is excellent in this department, and also provides a global benefit of drawing 3 cards per turn at a loss of only 2 life. Not only does this feel like a marginal downside early on, it also effects you-- which can be perceived as more 'fair,' and less threatening to the group. Oh how little the opponents know. They busy themselves with that sweet, sweet card draw.
The deck utilizes hand reduction geared toward your opponents with cards like Gnat Miser and Locust Miser, while allowing you an infinite hand size, through Spellbook, Reliquary Tower, and Venser's Journal--which also doubles as an outlet to bleed much slower than your opponents while Seizan is actively bloodletting the board. Use your tutors wisely to cover what bases you need covered. Keep in mind that due to Seizan's effect, you will see a lot of cards. Patience.
With respect to bloodletting, the deck provides many ways to bleed slowest. By the time this becomes relevant in the mid-late game, you will probably have been identified as a threat. When the group finally realizes that drawing half their deck isn't worth it anymore, they tend to smooth over any disagreements and band together against Seizan quickly. Venser's Journal nets large amounts of life, and targeted cards like Corrupt, Tendrils of Corruption, Gray Merchant of Asphodel, etc can be big bombs in recurring your life total. Bloodchief Ascension, an early Demon's Horn, and Blood Tribute help pad your life total out in the early-mid game before your opponents inevitably decide to throw off the yoke of bondage to Seizan, but that comes later.
While your opponents are drawing cards in the mid game, Seizan wants to restrict their hand size dramatically and painfully punish discarding. Liliana's Caress, Megrim, and Underworld Dreams all turn the card draw from Seizan ( kicked into full gear by Font of Mythos) into a painful pool of discard potential, made even narrower by reduced hand sizes via Gnat Miser and Locust Miser.
Cards like Psychosis Crawler are insane in several departments. You draw 5 cards with both Font of Mythos and Seizan active. 5 bleed damage to each opponent, Psychosis crawler gets +5/+5 and becomes a massive beater.
To round the deck off is a massive control suite, featuring many of Black's best options: Doom Blade, Dismember, Go for the Throat, Tragic Slip, Murder, Quag Sickness, and Stab Wound (providing secondary bleed) all make your opponent reel from deciding to turn anything sideways in your direction. When swinging is difficult and your opponents decide to join forces against you, Seizan switches into late game mode: direct damage/drain, and board wiping.
Once things get out of hand, Black features some of the most diabolical board-wipes in the game. Killing Wave, Life's Finale, Damnation, and Dread Cacodemon all clear the board out in the late game over and over again, and give you those last few turns you need to strangle your remaining opponents out.
There's a set of utility cards, Whispersilk Cloak to protect Seizan if need be, Gilded Lotus and Liliana's Shade fix mana if it's a problem (which is rare) Pain's Reward is fun to throw around for shock value and the general 'deal-with-the-devil' feel, and Liliana of the Dark Realms can make your manabase explode in the event that Dread Cacodemon is too difficult to hard cast, or if you need a bit more juice pumped into your life-drain spells.
Finally, add in a tutoring component to fix any holes you somehow haven't managed to draw into with Seizan's boundless wisdom--Diabolic Tutor, Demonic Tutor, Increasing Ambition, Beseech the Queen, Night Dealings--and you're golden.
Get out there and make your playgroup pay... slowly. That's the ticket.
