This is my friend's list but I wanted to play around with the list on my own as the deck is insanely fun. I've helped a little with the list in building it but honestly the full credit goes to him, you can find his original posting here, as well as his primer, which I have copied below. https://www.moxfield.com/decks/NsGaGdfW-kGi75eWGSbogw/primer
Feel free to ask questions though or give suggestions, as we are always looking to improve the deck.
Why the Commanders
Sakashima of a Thousand Faces This is the main Commander that we care about for this deck. It is not only one of our combo pieces but gives us access to some solid flexibility for longer and grindier games.
Vial Smasher the Fierce While this commander was mostly chosen since he is the only partner, we are trying to us Vial Smasher the Fierce as a temporary target for Sakashima of a Thousand Faces as well as a way to easily keep life totals of our opponents in check to make cards like Ad Nauseam and Necropotence worse. Also you can put curisoity on him to go full control mode if you have the right hand to support it.
Playstyle
This deck is trying to play a slower game using the all of the good answers that the Grixis colors offer to us. Then using our dragons to either stay ahead on resources or set up a combo win.
Plan 1: Dragonstorm
Cast Dragonstorm for at least three copies.
Put a two of the following into play: Scourge of Valkas, Terror of the Peaks, and Immersturm Predator.
Use the last copy of Dragonstorm to put Hellkite Courser onto the battlefield.
Sacrifice Sakashima of a Thousand Faces to Immersturm Perdator of kill it with the Terror of the Peaks/Scourge of Valkas enter the battlefield triggers if neccessary.
Use Hellkite Courser's enter the battlefield ability to put Sakashima of a Thousand Faces onto the battlefield as a copy of of the Hellkite Courser.
Repeat steps 4 and 5 as neccessary, using the extra damage from the Scourge of Valkas or Terror of the Peaks to kill your opponents.
Plan 2: Thoracle
We also have the Thassa's Oracle and Demonic Consultation/Tainted Pact package in the deck due to it being an extremely compact win condition.
Plan 3: Curiosity + Niv Mizzet
If this doesn't kill the table outright, you should be able to kill 2 other players, set your hand by drawing your deck, and either go for a oracle kill that turn with all of your deck in your hands or draw enough cards that you feel satisfied you can win the next turn with interaction up.
Plan 4: Grinding out the Game
Within boardstalls that happen due to multiple stax pieces or Rule of Law stye effects, the deck can also just outgrind other decks using the other dragons, such as Niv-Mizzet, Parun and Iymrith, Desert Doom to keep more resources than our opponents. We can also set up the combo shown above over the course of a couple turns since they are all creatures that can just be cast from the hand.
Setting Up the Mana Unlike most decks within cEDH, sometimes we want to hold our fast mana and use them more as rituals on the turn when we want to cast one of our dragons. This not only helps keep opposing Dockside Extortionists in check but also makes sure that we have the mana and storm count when we are casting Dragonstorm.
Overcommitting Storm Count It is important to try to have excess copies of Dragonstorm on the stack besides the three that are needed to win the game. This is because, unlike other Storm decks, they can just counter one of the copies in order to stop us from wining the game. It also allows us to set up some protecting by putting Niv-Mizzet, Parun or Dragonlord Silumgar into play first to act as protection from spot removal.
Single card discussion:
Dockside Extortionist: This is easily one of the strongest cards in the deck. Just be careful and make sure to double check the battlefield before you cast it.
Jeska's Will: While both modes can be extremely good, if you are trying to cast Dragonstorm: either make sure that none of your targets are in the top three or you can also just choose the mode to make mana even if you have a commander in play.
Mana Drain: Sometimes it is necessary to snap counter something even if it is for one or two mana in order to have enough for your next turn. However, don't feel the need to hold it until it is too late as it is just a counter spell.
Chain of Vapor: Similar to Mana Drain, this can be a defensive tool that can also bounce your mana rocks or Dockside Extortionist for more mana as well as put enough cards into your graveyard for threshold on Cabal Ritual as well as give you more Escape fuel for Underworld Breach.
Curiosity: This is mainly for Niv kill, but it should be noted you can always throw it on Vial smasher to turn into a harder control deck depending on the board state and your hand. With interaction up you can draw a lot of cards very quickly. This really helps grind out your games if need be against hard control.
Intuition: Unlike other decks in the format, our Intuition can be an incredibly flexible. Whether getting interaction needed for the current board state or setting up a Underworld Breach/Yawgmoth's Will.
Spellseeker: This creature allows you tutor chain with Demonic Tutor or find a needed ritual or piece of interaction for the next turn.
Dark Petition: This card acts as a second copy of Demonic Tutor but has the added benefit of being five damage with Vial Smasher the Fierce.
Final Parting: This card acts as one of the strongest tutors in the deck. This is because you can entomb Dragonstorm and find Mizzix's Mastery in order to cast Dragonstorm for three copies without any other cards.
Notable Exclusions
Ad Nauseam: We are not playing this due to having so many higher mana costs in our deck. It just doesn't draw as many cards as we need it to.
Peer into the Abyss/Necropotence: This is a control deck and as such doesn't have the tools necessary to capitalize on the power of these cards properly.
