Wanted to create a thread/primer for the deck commonly referred to as 8-rack. While not all versions run 8 rack effects anymore, the core of the deck's strategy remains the same: get your opponent hellbent as quickly as possible and let The Rack and/or Shrieking Affliction quickly close out the game. The addition of Urza's saga helps push up the power level of this deck by giving it an (essentially) uncounterable tutor for racks or grave hate while also providing an option for jamming up the board with some potentially large construct tokens.

Some of the common cards used are listed below for people who may not be familiar with the deck, as well as a list I am currently using that is completely untested in the arena. I've only been able to playtest it but I would like some feedback on it.

Murderous Rider - Deals with creautres or planeswalkers at instant speed, can leave behind a body that recoups life loss and hides from discard until you are ready.
Plague Engineer - Great against go wide X/1s, probably doesn't need much introduction here.
Nether Spirit - When ran, usually ran as a 1 of and the only creature.
Bloodghast - Great to add pressure, downside is they can't block.
Rotting Regisaur - Fatty that works well in a hellbent environment, which this deck often finds itself.
Dark Confidant - commonly ran in the sideboards for the decks that grind a little bit better or where card advantage is needed.
Scourge of the Skyclaves - Newer card, not commonly seen, but can act like a 2 mana goyf, especially with thoughtsieze.
Dauthi Voidwalker - Newer card, acts as gravehate with some shenanagins.
Hex Parasite - Plays well with Urza's Saga and helps deal with opponents Chalice, which can prove to be a big problem for this deck.

Discard - 1 mana:[/cards]
Thoughtseize - Classic. Often a 4 of if IoK is not used.
Inquisition of Kozilek - Also a classic, often a 4 of if Thoughtseize is not used.
Raven's Crime - Very good card for this deck as it turns late game land draws into discard.
Funeral Charm - flexible card that has seen some resurgence of late. Kills x/1, acts as 1 for 1 discard and can give a construct token swampwalk with an Urborg out to close out the game quickly.
Duress - Older card, not seen much anymore due to better cards but it isn't a terrible choice. Hits artifacts, enchantments, and planeswalkers which are tough for this deck to deal with.

Discard - 2 mana:
Whispers of Emrakul - I've never seen anyone run this but I feel like its worth a test. Getting 1 or 2 cards at random can be strong. Given that half of our other discard is at the opponent's choice, it isn't any worse (except for being 2 mana) and often is better.
Wrench Mind - 2 for 1 in modern (most of the time).
Collective Brutality - Flexible answer to deal with x/2's and get instants/sorceries out of your opponent's hand. Occasionally the 2 life drain is useful. This card tends to be strong vs burn.
Liliana's Triumph - Instant speed edict that occasionally acts as discard as well.
Smallpox - Tempo swinger that can really cripple decks when played right.
Mind Rake - Can be cast with overload to get around leyline of sanctity.

Other discard:
Delirium Skeins - used to get around the same leyline of sanctity.

Removal - 1 mana:
Fatal Push - Standard black one mana, instant speed removal. This deck doesn't usually run fetches so it can be awkward at times were it isn't able to be used.
Funeral Charm - Gets all those pesky monkeys running around.
Innocent Blood - Other standard black one mana edict.
Bloodchief's thirst - Targeted removal for creatures and walkers. Can be a bit mana intensive.
Dismember - often seen as a 1 of for quick removal of a large threat.

Removal - 2 mana:
Sudden Edict - uncounterable instant speed edict.
Collective Brutality - see above, deals with x/2 creautres.
Liliana's triumph - see above as well.
Smallpox - see above.
Damn - Sorcery Speed, unconditional removal.

Other Removal:
Baleful Mastery - Flexible on the tempo aspect, but good in that it exiles.
Murderous rider - 3 mana which can be steep for this deck but hits everything.
Bontu's Last Reckoning - 3 mana Board wipe at hte expense of your next turn.
Damnation - Board wipe with no conditions.

Urza's saga targets:
The Rack - the namesake of the deck. You will probably always want 4 of these with Urza's saga.
Nihil Spellbomb - 1 of for Grave hate. also cantrips.
Pithing Needle - Great for walkers or other problem permanents.
Expedition map - kind of an odd choice but it allows you to fetch up your next saga.
Hex Parasite - see above.

Liliana of the veil - Needs no introduction. Discards, edicts, and should probably be a 4 of.
Liliana, waker of the dead - Newer card, acts as LOTV #5, but the 4 mana is a big ask for this deck.
Ashiok, nightmare weaver - Grave and fetch hate, alternate win con.
Davriel, rogue shadowmage - Rack options 9-12, or a budget LoTV.

Rack effects:
The Rack - see above.
Shrieking Affliction - Enchantment version of the rack that hits harder when opponents are at 1 card in hand.

Other/Sideboard cards:
Leyline of the void - grave hate
Surgical Extraction - grave hate
Cling to Dust - grave hate, with an added bonus of late game card draw or life gain.
Tormod's Crypt -can also be tutored with saga.
Ensnaring Bridge - given as most games get both players hellbent, this stalls out and lets the racks deal their passive damage.

Mana base:
Urborg, Tomb of Yawgmoth - helps utility lands tap for black.
Mishra's Factory - Standard man land that can pump construct tokens.
Urza's Saga - New card, very powerful. Spams the board and tutors up racks and puts them directly into play (or needle, or spellbomb)
Bojuka Bog - simple grave hate.
Castle Locthwain - Card draw.
Hive of the eye tyrant - New man land with a little bit of late game grave hate for when that is an issue.
Silent Clearing - Most decks are mono black but still include these for some late game draw if needed.
Nurturing Peatland - see above.

If there are others I am missing, please let me know and I'll add them to the list.