Landless Dredge

Key Interactions-
Balustrade Spy + Dread Return and No Lands
Phantasmagorian + Phantasmagorian or Nether Shadow or Dredgers
Flayer of the Hatebound + Golgari Grave-Troll or Cabal Therapy
Nether Shadow + Dredgers
Street Wraith or Gitaxian Probe + Dredgers

Landless Dredge has two very important rules that can almost never be broken. Unlike pretty much any other Magic deck out there, you can almost never mulligan and you always want to go second. Why? So you can abuse the maximum hand size rule of course! The maximum hand size rule is an easy and un-counterable way to get your initial dredger (or Phantasmagorian) into the graveyard without the use of any mana! From here on out it's a game of Magic all its own. If things go your way you will never use your draw phase to draw a card ever again. Instead, you will use your dredgers to fill your graveyard and empty your deck. From there, you will reanimate Ichorid and Nether Shadow as often as possible. These recurrable threats (along with Narcomoeba) act as Cabal Therapy food to disrupt your opponent's hand, and fuel for Dread Return, which hopefully targets Balustrade Spy. Because you have no lands reanimating Spy means milling your entire deck, leading into additional Golgari Grave-Troll, Flayer of the Hatebound, and Chancellor of the Annex resurrections. Of course, any of the Dread Return targets can be used as powerful finishers even without the spy. All of this sacrificing is made stronger with Bridge From Below, which can act as a very powerful win condition as well.

Gitaxian Probe and Street Wraith speed things up by providing multiple dredges a turn if they happen to be in your hand, with the Wraith also acting as Ichorid food once he has done his job. These cards can also be replaced with Urza's Bauble and Mishra's Bauble, but I prefer looking at my opponent's hand and feeding Horrors. Cabal Therapy is your disruption, which also provides a sacrifice outlet for Bridge activations. With multiple Bridges in your graveyard a single Cabal Therapy can create a drastic advantage in your favor. Sickening Shoal takes up one of four flex slots that can make a use for extra Phantasmagorians in your hand, turning them into a way to deal with troublesome creatures. Contagion is another option that fills the same role, with both being played in varying numbers. The other three slots are occupied with Chancellor of the Annex, who helps prevent turn one hate spells form your opponent such as Thoughtseize or Relic of Progenitus and can also be Dread Returned against combo and other strategies. Gigapede has also been played in the past, acting as another discard outlet that can combo pretty well with Phantasmagorian.

Of course, as a deck that eschews from using lands you can bet your buns that it has some pretty neat interactions to master. The first set I'm going to mention are in relation to Phantasmagorian. By himself, Ol' Gory can simply be used as an instant speed discard outlet, easily stacking creatures in your graveyard to make Nether Shadow activations easier. Because of the structure of his discard ability you can also use his ability in response to itself, allowing you to discard multiple sets of 3 cards with the same Phantasmagorian. In this same vein, you can use two Gories together to discard two cards at instant speed as many times as you'd like, discarding one Phantasmagorian to the other every time. Finally, when combined with Street Wraith you can discard a dredger with Phantasmagorian, respond with a Street Wraith to dredge it, and then discard that same dredger again with another activation of the same Phantasmagorian's ability.

Probably the most confusing trick at your disposal is one that comes up from playing what is one of the only reasons the graveyard order rule exists: Nether Shadow. When in the graveyard Nether Shadow needs creature cards above him in order to be resurrected. As you probably know, it is against the rules to re-arrange the order of your graveyard, so this kind of "cost" can be difficult to achieve at times. What makes this easier to accomplish is a little known ruling in relation to dredging. Rule 404.3 states "If an effect or rule puts two or more cards into the same graveyard at the same time, the owner of those cards may arrange them in any order." What this means for us is that whenever you dredge (or discard him to Gory) you can put him as far down in that group of cards as possible. Since you discard or Dredge as a single ability all at once, this is entirely legal. Dredging six cards with Golgari Grave-Troll and you hit a Shadow? Put him at the bottom of those six before you throw all of them into the graveyard. This will allow Shadow to come back much more often than he normally would be able to.

Finally, as always you want to try and learn how Bridge From Below triggers work as concretely as possible. Knowing how and when Bridge triggers, who gets Zombies and who doesn't in any given situation is an extremely important aspect of piloting this deck. Common questions come from trading creatures in combat, losing a creature in response to a Cabal Therapy or Dread Return and knowing what happens when your opponent has a Cursecatcher in play. These questions and more have all been answered in the past by multiple writers, so a quick use of Google or adventure to a Dredge primer can help you to study up.

Sideboard Suggestions-
As with every deck in this article, the absence of lands means that your options are pretty limited when it comes to the sideboard. Leyline of Sanctity and Leyline of the Void are nice when it comes to opposing combo. Tormod's Crypt, Ravenous Trap, Mindbreak Trap, and Chalice of the Void (being set to zero) are additional options.

Aggro matchups are best dealt with using cards like Contagion and Sickening Shoal, depending on your numbers in the main board. There are a few key fatties that favor you in these games as well, these being Elesh Norn, Grand Cenobite,
Llawan, Cephalid Empress (for Merfolk), Ancestor's Chosen (for burn and similar strategies), and Stormtide Leviathan/Blazing Archon.

Control is one of your best matchups because most of what you do is uncounterable. Even then, Cabal Therapy will make sure they can never hold a counter when they need it. That being said, it is never bad to have something. Terastodon or Sylvan Primordial can help against permanents like Moat or Solitary Confinement. Iona, Shield of Emeria can blank their removal or win condition colors too.