Big picture
use grenzo as a resilient value engine and playmaker to churn out pieces for combo and interaction. this list can win through critical mass or combo, seeking to assemble overlapping combo pieces or overwhelm with value.
Building mindset
cut the fat and focus on setting up wins while leaving plenty of room for pet cards. this deck is built to be a 7-8 power, set to kill but non-powered and with some unfocused cards. while it's competitively geared, you're not playing many staples and it's primarily centered around the warden himself.
Notable features
doubly dead
a package of persist and undying creatures unlock numerous lines to victory utilizing Yawgmoth, Thran Physician and Mikaeus, the Unhallowed. Putrid Goblin and Butcher Ghoul provide value early and go infinite late while Puppeteer Clique and Furystoke Giant strike a middle ground, providing heavy utility while still furthering your win. To support this, you do need an expanded sac package with Carrion Feeder, Sadistic Hypnotist and Goblin Bombardment. Honestly, you might might want more and could consider the altars to power up a bit.
tucked in
for setting up grenzo, we're looking to make all of our pieces either large scale or small opportunity cost. on the small end Conjurer's Bauble and Tel-Jilad Stylus are low cost and even enable your welder package. meanwhile Teferi's Puzzle Box and Mindmoil hope to be worth their while by setting up entire combos in single stacks. Seer's Lantern and Vessel of Endless Rest are acceptable middle grounds albeit far from essential. A notable addition here is The Cauldron of Eternity which enables all sorts of nasty loops and goes infinite with Priest of Urabrask and a sac outlet. Great welder hit too.
buckle up
grenzo is mana hungry in colors with poor fixing. Much of this ramp is tucked into creatures (Ornithopter of Paradise, Burnished Hart, Palladium Myr) to help with grenzo hit density but some rocks are necessary. Fires of Invention should go a long way here, potentially allowing you to double spell while still sinking your mana into the warden.
on not dying
it's kinda hard to interact in rakdos. you get the best wipes in Toxic Deluge, Fire Covenant, Blasphemous Act and Vandalblast but struggle to interact 1:1 at instant speed at any rate better than Doom Blade. Snuff Out and Chaos Warp are your best panic buttons and Deadly Rollick would obviously be welcome if you're into that. Otherwise, we're trying to lean on the creatures and set up Duplicant, Plundering Barbarian or even Flayer of the Hatebound to hit key pieces.
Finds
Thran Turbine. the use is obvious. this isn't great, but it's powerfully on theme and is a great thing to swap with a Bolas's Citadel. as a 1 drop, it does have a theoretically pretty high output over the game.
Furystoke Giant. wtf is up wit this guy? he stokes your boys into throwing. this kind of effect will really wreck a deck like lurrus and commander seems to be swarmed with those kinds of value creature decks. and late, he goes infinite with mike.
Clone Shell. this dude kinda does it all for you. it digs for a combo pieces and lets you hold it up at instant speed with a sac outlet. at the same time, it's stacking your bottom, setting up further dungeoneering. it gives you a lot of control and could enable some pretty tricky instant speed wins. goes absolutely insane with The Cauldron of Eternity.
Stomping Slabs. did not burden you with this in the list but it does stack your bottom 7. kinda lit.
Dying words
i'm hoping with this build to have a focused plan which you can aim for each game, helping to counteract the inherently random nature of the commander. i think the larger bottom of the library set ups should help with knowing when to invest big with grenzo in it a way that individual scry 1s can never produce. it seems like the deck presents lots of complex and powerful lines when considering the battlefield as well as the top and bottom of library, often with good ability to shuffle those around.
it could be argued that pure set up pieces like Conjurer's Bauble and Teferi's Puzzle Box could be better replaced with actual hits for grenzo, though honestly you run out of things you really want to hit unless you start feeling like you need more Shriekmaws. more importantly though, i'm not sure it's ever going to be a great line to just be activating grenzo blind as you only hit 1/3 of the time which is pretty awful. as such, it may be better to focus on the efficient set ups and using grenzo mostly to cheat for mana and cards rather than as a mana sink. the power of his effect is that it's 2 mana to both "draw" and "cast" the creature. it's insane when it hits, but when it whiffs it does literally nothing. like, grenzo can win with 4 mana at instant speed with a Mikaeus, the Unhallowed and Triskelion on the bottom but will see only 1/2 of a random creature on average when investing blind. this is all to say that it seems to me best to orient the deck around good tuck set ups and only moving to grenzo when you have hits in the bank.
finally finally, on power, it's a bit frustrating. the deck only has 2 hits above 3 power. Flayer of the Hatebound and Mikaeus, the Unhallowed. it's frustrating that they're both quite important. my guess is that playuing grenzo for 3 will mostly be the play as it's relatively easy to reanimate or retuck these few targets. at least Cloak and Dagger somewhat helps address the issue.
it's been a fun thought quest to work on this deck regardless of how you end up building it. good luck
