My grenzo deck, with slight restrictions. I made the deck with the intention of running as many creatures as possible, and as few non creatures spell as possible, to maximize grenzo efficacy. The deck is built to maximaze grenzos ability. The non creatures I run are what Ive found to be invaluable in the deck.

C&C encouraged

Flayer of the Hatebound - Anything Grenzo brings out gets a trigger from him

Devil's Play - Flashback is good for when grenzo puts it into grave, also a win con with infinite mana

Reito Lantern - Infinite mana with Su-Chi and Ashnod's alter, should really be a soldevi digger, so that it could make infinite mana with priest of urabrask and cothodian as well

Deathbringer Thoctar - Infinite Damage with Mikhaeus and sac outlet

Cathodian - Infinite Damage with Ashnods alter, reito lantern and blood artist/flayer, also many synergies with reanimation and sac effects

Volcano Hellion - With stuffy Doll, Kill opponent with less life than you

Feldon of the Third Path - Enables combos that are in my grave easily, very powerful

Puppeteer Clique - Steal whole graves with Mikhaeus

Balthor the defiled - Well Duh

Nekrataal - Good control that grenzo will always hit

Shriekmaw - Same

Zealous conscripts - Kiki combo

Worldgorger dragon - The only creature with power greater than 6 in the deck, so grenzo never goes that high. With Animate dead, and secondary target in grave, infinite mana

Su-chi - Infinite mana with reito lantern and ashnods alter, also very good with soldevi adnate

Solemn simulacrum - Ramp that grenzo will always hit, also works well with soldevi adnate

Soldevi Adnate - Honestly probablly my favorite card in the deck. Can send your mana into nuts territory very quick

Sidisi, undead vizier - When grenzo hits her, its a recurable demonic tutor

Rakdos, lord of riots - Can make grenzo as big as you like

Precursor golem - 9 power for a grenzo activation is good, plus good synergy with ashnods alter and soldevi adnate

Pack Rat - Can be a big threat on board, as well as putting bombs in my grave to combo out

Overseer of the damned - The only unconditional creature kill with a body that I know of

Necrotic Ooze - Kiki+Mogg Fanatic in grave, infinite dudes, infinite damage

Murderous redcap - Infinite Damage with Mikhaeus and sac outlet

Molten Primordial - Very useful etb trigger for grenzo

Merciless executioner/fleshbag marauder - Pure value when grenzo hits them

Juntroller - Allows for recurring etb effects

Falkenreath aristocrat - Sac outlet plus great meat shield

Canal Dredger - Another Junktroller

Butcher of Malakir - Can easily opponents fields

Bogardan Hellkite - Good Etb trigger

Body snatcher - Very good reanimation and grave filler

Bloodfire Colossus - The best board wipe with a body I could find

Big game hunter - Nearly unconditional removal

Crucible of worlds - Grenzo hits land occasionally, so might as well get some value out of that. Could also play one of the 8 fetchlands in the deck every turn, thinning the deck for grenzo activations

Ashnods Alter - Can cycle through a huge portion of my deck if I want a big grave

Victimize - Often allows for a turn 4 win by returning a combo from grave