This is my Competitive Grenzo list. Based around using Doomsday to create a winning stack of cards. The typical Doomsday stack consists of (top to Bottom)
Flex cardZealous ConscriptsMad AuntieKiki-Jiki, Mirror BreakerPriest of Gix
This stack lets you use Grenzo, Dungeon Warden's ability to put the Priest of Gix in play, then get Kiki-Jiki, then copy the priest leaving mana floating, this allows you to get Mad Auntie (boosting Grenzo's power to 3 if he's at 2, another note: if you have enough mana you can copy Mad Auntie with Kiki-Jiki, Mirror Breaker to regenerate him or Grenzo.) and then getting Zealous Conscripts allowing you to get an infinite number of conscripts. Feel free to use Priest of Urabrask or Treasonous Ogre in place of Priest of Gix when appropriate. You should NEVER play doomsday and pass the turn, you will not survive until your next turn. You always want to leave 2 mana up to combo out. If you have more mana up you can use Phyrexian Rager to draw a card to protect your combo (such as Imp's Mischief).
Another main combo in this deck is Animate Dead + Worldgorger Dragon . This makes an infinite amount of mana(if you don't know how this combo works check out This), and allows you to get out your entire deck on the battlefield with Grenzo. Keep in mind that you will need another creature card in your graveyard, or Grenzo on the battlefield to end the loop.
The third main combo is using Buried Alive to get Necrotic Ooze + Phyrexian Devourer + Triskelion in the bin. Then use a reanimation spell on your Necrotic Ooze, this will give him the ability to continually put counters on him with Phyrexian Devourer's ability then remove them with Triskelion's ability to do an amount of targeted damage equal to the combined CMC of the cards left in your library.
Another combo, that, admittedly, I have never used, is playing a Fire Covenant on a Stuffy Doll. This only works if you have more life than the selected player, and it only kills that one player.
When piloting this deck one must first decide which combo to pursue from looking at the opening hand. Usually, Doomsday is the most efficient route, but reanimating Worldgorger Dragon is also fairly easy. If your opening hand has Insidious Dreams, then you should pursue the Worldgorger Combo. With Insidious Dreams discard 3 cards and set up the top of your library like so:
Faithless LootingAnimate DeadWorldgorger Dragon
This will allow you to get Worldgorger in the grave, then immediately bring him back with Animate Dead, winning you the game. Another way to use Insidious Dreams is as a Pseudo-Doomsday by discarding 5 cards and setting up the top of your library with:
Surging FlameKiki-Jiki, Mirror BreakerZealous ConscriptsMad AuntiePriest of Gix
Surging Flames puts cards on the bottom of so you can Grenzo them out and win.
This deck tries to protect its combos using targeted discard effects such as Duress, and Distress. This can be problematic at tables where there are more than one control player. Another way to disrupt your opponents is through Blood Moon or Magus of the Moon (which I do not have enough money to buy), although this deck is still weak to Mono-Blue decks like Azami, Lady of Scrolls or Talrand, Sky Summoner.To win on turn 1 you need to do the following.
Play an untapped red land, play Faithless Looting discarding Worldgorger Dragon+ any other creature. Then, play out Lotus Petal crack it for then use the black to play Dark Ritual, you should now have floating, use that to cast Animate Dead/Necromancy/Dance of the Dead. Now you have infinite mana and can easily win.
If you want to look further into this deck, check out the primer here
