Disclaimer
I know that Griselbrand is banned in multiplayer EDH. I just wanted to create a decklist to see what it would look like if he was unbanned. If you truly want to play this deck, just play Sidisi, Undead Vizier as your commander instead, and everything should be fine (strategies will be explained later on).
A little bit about me
Before advancing to the primer, I think it might be a good idea to write about my experience as a player. I started collecting cards while I was young, but only for the art: I had nobody to play with. As I went to highschool, I made some new friends and they introduced me to EDH. My first ever deck was The Mimeoplasm on a really, really tight budget. It was a gift from one of my friend and I had load of fun with it. The first deck I built by myself was mono-green goodstuff Omnath, Locus of Mana. It was pretty good at the time, generating lot of mana and tokens. I had to quit playing for some time because of some problems in my life, but when I got back, I heard about cEDH.
I started creating some more competitive decklists, and I also updated a list of commanders by tier ([List - Multiplayer] EDH Generals by Tier) since. I am really involved in cEDH now, and I like to create new decklists. My interest for Griselbrand comes from a mono-black storm list I saw with Sidisi, Undead Vizier as the commander (link here), and I based myself on it to try to improve it.
For both decks, the game plan (it will be convered in details later) is pretty similar: ramp really fast into your commander, then draw a shitload of cards and build up a lot of mana and a high storm count from there. The only difference is the way they have to do it:
Sidisi, Undead Vizier relies on Ad Nauseam to draw most of her deck. You ramp into her, then sacrifice her to search for your win spell.
Griselbrand relies on nothing but himself. Yes he costs more mana, but this will be covered by the turn it takes you with Sidisi, Undead Vizier to fetch Ad Nauseam. Once he lands, you can draw up to 35 cards (depending on your life total and what your opponents are playing, sometimes you want to keep a some safety). He can also have Ad Nauseam in the deck as a backup way to draw your deck if all else fails, and it is fairly easy to tutor because of the color identity. he can also gain some life back in only one swing, and commander damage is not something impossible to achieve with him.
Once you no longer have enough life points to continue drawing, you start chaining spells to get a lot of mana to win through either Tendrils of Agony or Exsanguinate. With Griselbrand, if you don't have enough mana/storm to kill everyion in a single strike, you can restart drawing at the cost of life, which you should have plenty now that you drained everyone. With Ad Nauseam, you would need to cast it again, and you are limited to two times (because of Yawgmoth's Will it would be exiled after the second time). So Griselbrand lets you start back the drawing engine, while it is harder to start it back with Sidisi, Undead Vizier, and would cost more mana to do so.
Griselbrand costs 8, but can start drawing the turn he comes into play. To do the same thing with Sidisi, Undead Vizier and Ad Nauseam, it would be the equivalent of 10 mana, which would be more difficult to obtain faster.
Cards selection
So this is a storm deck. In multilpayer. In 1vs1, it is way easier to kill an opponent because the storm count needed is smaller. Also, we are playing this one mono-black, so we don't have access to wheel effects or other cards that would make Grixis Storm so good (link here). So we need to be a little more creative when it comes to select cards for the deck. Also, since a backup (or main, depending on the commander you play) is Ad Nauseam, we need to keep a low CMC to be able to draw a lot of cards at once.
The first category of cards that are essential to the deck are positive mana rocks. What do I mean by positive mana rocks? Artifacts that cost less than what they produce and that don't require another for of initial investment (by investment, I mean something like a multikicker for example Everflowing Chalice, I do not consider it as a positive rock). In the 0CMC rocks, the only one I left out for now is Lotus Bloom because we need to wait to get mana, and we want to get the mana ASAP. Maybe it is going to be included later but I will need to playtest. Also, there are not only the 0CMC rocks, also the ones that cost less than what they produce, like Sol Ring, they will net a positive amount of mana, even if it only is one, you want to cast more cards for the storm count. Voltaic Key, while not being a mana rock by itself, does combo with positive mana rocks (that are producing more than one mana to untap them and generate even more mana. Also, all 1CMC artifacts will net positive mana with Krark-Clan Ironworks, so this will never be useless.
Black also has access to some good rituals that will net more mana than what they cost. Some will also require you additional costs, like sacrificing creatures, but this will be covered in the next section. You don't mind sacrificing some of your resources, like creatures or lands, because this is an all-in strategy: you want to win in a single turn.
Ok so for the creatures, here is the trick: you play all the 0CMC creatures that will not die upon entering the battlefield, so no X costed creatures. There are actually 4, and they are all also artifacts, which is relevant for one of the way to generate a lot of mana that will be described later on. They will be used for all the effects requiring a sacrifice, and since they cost 0, they will also up the storm count and they will help you generate mana in various ways. For example,
Culling the Weak
, Songs of the Damned are two good uses for them.
Now, time to improve the land base a little. Since the strategy is to ramp up to our commander as fast as possible, we also want to get some lands that can tap for more than one mana to get it faster. This time, it is not important if the land comes into play tapped or will have to be sacrificed; once our commander is in play, we can draw and will no longer need them. So, everything that can tap for more than one mana but will not loose me the tempo (nothing that can't produce mana as it enters like Temple of the False God or that will bounce a land like
Everglades
) is a good inclusion. Some lands are also included for specific protection against specific colors. Cavern of Souls will be in there specifically against blue decks to get an easy way to prevent your commander from being countered. Urborg, Tomb of Yawgmoth is in here for the single purpose of turning all your nonbasics into swamps so they can be sacrificed to
Lake of the Dead
. Darksteel Citadel and Vault of Whispers have been included simply for the fact that they are artifacts that can be sacrificed to Krark-Clan Ironworks to get more mana if they were your land drops earlier. Reliquary Tower I think is really obvious, just to keep cards in your hands if you ever have to wait a turn (same for the artifact version, Spellbook).
I almost forgot, but we need to add some cards that will be our actual win conditions and backup plans. Those are the cards you will generate storm count/high mana for. Those are the cards that will help you draw and get a lot of mana. Those are the cards you will use your tutors for if you don't already have them in your hands.
I also forgot to add the best thing available to black: tutors. Basically, they will be any card in your deck, just tutor what you need to continue adding to storm count while also searching for any missing card. The best tutors in this deck are the ones that can search for any card, and that will put the card directly into your hand, as you would need to draw a card to get it into your hands with the others. This does not mean they will not be included, just that I think they are generally weaker tutors. Also, there would be a trick to get the card in your hands: cycling lands. I could tutor, then cycle to draw the card freshly tutored. Usually, if before Griselbrand, the tutors can be used to fetch something that will help you ramp real hard, like
Lake of the Dead
, or if you can go for it, Ad Nauseam instead of your commander (you can still cast him later if you need to keep on drawing after gaining life out of your two main kill spells). Expedition Map usually tutors for
Lake of the Dead
, as it helps me accelerating so hard it is not even funny.
Win conditions
The first and obvious one is storm with Tendrils of Agony. Cast as many spells as possible, then get a lot of copies of it. Draw more cards if needed after, then play it again because of Yawgmoth's Will.
Second one would be to generate as much mana as needed to kill everyone off of Exsanguinate. Don't be afraid to continue drawing cards after gaining lot of life if it was not enough and cast it back after Yawgmoth's Will!
Third would be to combine both first and second to generate high storm count, lower life totals with Tendrils of Agony then finish off with Exsanguinate. Don't be afraid to cast them multiple times with Yawgmoth's Will!
Fourth one is a backup win condition: Basalt Monolith with Rings of Brighthearth to produce infinite colorless mana for Exsanguinate. The rock is also a neutral, so it would up the storm count without loosing mana, and the rings can help you activate Griselbrand a couple more times at the cost of only two colorless instead of 7 life.
Cards that are not main for now and why (also cards that will maybe get the cut)
So, life is an important resource for this deck, as it is what will allow me to get cards into my hands to storm. Everything that consumes life for useless purposes will not be included such as fetchlands. Also:
Grim Tutor
because I loose 3 life (also because of the pricetag but that is not the main argument). But I will playtest as I would still be able to draw 35 after this, and it could be good to have more tutors.
Vampiric Tutor for now not in because of the 2 life loss, but probably will come in because how good this is also before Griselbrand.
Imperial Seal... Ok well because of price tag, because it is kind of Vampiric Tutor number 2. Will playtest with it for sure and proxy it in paper ;)
Ancient Tomb maybe will get the cut, because I try to avoid it to keep my life total high enough to draw as most cards as I can (35) when Griselbrand lands. Still, with no other life loss I would still be able to do it, but I would be in Lightning Bolt range and that makes me uncomfortable... Still keeping it for now because it can greatly help accelerating.
Commander swapping
So as you may already know, unfortunately (no there is a reason), Griselbrand is banned in multiplayer commander. If you playtested this deck already, you might have noticed that it is possible to win on turn 2 to 4, simply by casting Griselbrand out of the command zone, then storming. That is why if you want the deck to be legal, you will have to switch using Sidisi, Undead Vizier as the commander. Here are also some replacements I would do, because some cards are in here because of Griselbrand:
