"Death's Shadow Voltron" might be a bit misleading, because DS is actually used as a Scavenging source with Varolz, the Scar-Striped. By only paying B you get 13 +1/+1 counters on any of your creatures and that's it basically.
Here are the roles each card fills:
Combo Pieces
-Varolz, the Scar Striped and Death's shadow are the main combo pieces. 4 of each makes it so that you'll almost always be able to get them together in a game.
-Bayou Groff is a new addition that helps the deck in the case that the graveyard is limited, and also acts as a good scavenging source with 5 counters for 1G.
Scavenge Targets
There are multiple "voltron" targets in this deck. Nether Traitor, Nullpriest of Oblivion, Valentin, Dean of the Vein, and Inkmoth nexus are all great scavenge targets and keep the combo options open.
Combo Protection and Disruption
-Spellskite is very useful for protecting the important creatures, and comes in handy when it hoses certain matchups. With the prevalence of red decks right now, being Lightning Bolt proof is very strong as well.
-Apostle's Blessing serves the same purpose, but opens up alternative plays with protection giving evasion to swing for lethal.
-Maelstrom Pulse, Abrupt Decay and Golgari Charm are good catchall disruption against combo decks and can remove troublesome permanents like Leyline of the Void or Ensnaring Bridge.
-Thoughtseize is by far the best card in the deck and the best form of interaction. It gives us vital information to combo off safely, and also slows down other combo decks.
Self Mill
Self mill is another important part of this deck, as a lot of play happens out of the graveyard. When looking at my opening hand, I mainly look for a way to get Varolz in my hand or in play, and plan to mill Death's Shadow into my graveyard using these cards.
-Stitcher's Supplier is the best mill for the mana investment and provides a sacrifice outlet for Village Rites, Varolz, or Bayou Groff.
-Witherbloom Command is doing incredible work as well, often functioning as a 2-for-1 while filling the graveyard.
-Satyr Wayfinder serves the same function while providing another body.
Combo Enablers
This section is the most flexible to being boarded out because some matchups may call for a slower combo that comes at the end of a grindy game.
-Unearth is insanely good in this deck. More and more options come up as the graveyard fills and Unearth can reanimate any creature in the deck. This is most likely the first card to be boarded out in game 2 when GY hate is expected.
-Eternal Witness is just a solid card as a one-of and combines very nicely with Unearth to bring back a creature and any card from your graveyard for B.
-Grisly Salvage is mostly to dig for Varolz and fill the graveyard, but it also helps to make land drops if you already have the combo.
-The singleton Village Rites is just to give the Stitcher's Suppliers and Satyr Wayfinder a little more usefulness, or to take advantage of a creature that an opponent is trying to remove.
Mana Base
The mana base for this deck is somewhat budget, but IMO fetchlands are wholly unnecessary for this build. This deck functions very well with the land choices here, and 21 lands seems to be the sweetspot. Even with 2 Inkmoth Nexus I rarely find myself starved for colored mana.
Shizo, Death's Storehouse is also an automatic include as a 1-of because it has no downside, and can make Varolz unblockable in a pinch (against Ice-Fang Coatl for example).
Sideboard
The sideboard for this deck is mostly based on the current meta or what this deck struggles with. Aggressive prowess strategies are probably the toughest matchup to combo off against without dying first, and those decks are quite prevalent right now. Control can also be oppressive and very hard to play around with this deck.
-Lifegain from Gnaw to the Bone (and the lifelink creatures) is very good against the aggressive red decks
-The 2 Fatal Push are mostly insurance against the Lumimancer decks at the moment
-Tribal type decks get hosed by Bile Blight
-4 Veil of Summers are absolutely necessary to combo off against control and discard.
-Some light graveyard hate comes from the Nihil Spellbomb and Grafdigger's Cage when needed.
-Force of Vigor and Masked Vandal are more niche sideboard cards for matchups like Hardened Scales and Heliod Company.
-The two Duress in the sideboard are also niche cards meant to help stop decks that combo off with spells (Electrodominance/As Foretold, or various types of Storm)
Comments on Resilience
I know what you're thinking, this combo seems really fragile and inconsistent. In the months that I have playtested and piloted this deck, I have gotten better at playing it properly and I can confidently say that this combo is quite resilient. Even with a Nihil Spellbomb on the field, you can still combo off with no possibility of your opponent interacting. Basically, if you are able to resolve Varolz, you are able to make a 14/14+ creature.
I have played around using hexproof creatures like Silhana Ledgewalker as scavenge targets, but I would often hit my opponent for 14, then not be able to finish off the remaining damage. I found that with protection in the deck it is much better to scavenge onto creatures with more applicable keyword abilities and gain value from that. Nether traitor being practically unblockable, and the lifelink creatures gaining you 14 life is the type of swing that makes it so that your opponent has limited options after the hit connects.
