In The Beginning:
By the title, I bet some of you thought this was all about zombies, didn't you? Well, not this time. It's about dying and then not being dead. That makes sense, right? Basically, because of Solemnity, you are able to sacrifice creatures with Persist or Undying without their counters being placed on them after they come back to the battlefield; which allows you to sacrifice them as many times as you want. I am not the first person to use the combination of these cards and I won't be the last. There are many, MANY more ways to make these cards and other cards work in different ways to accomplish fun and interesting combinations to win your game. It's one of the innumerable aspects of this game that make it as incredible as it is. Thanks for reading my bullshit. Carry on.
Phyrexian Unlife stops you from losing the game when your life total reaches 0. What happens then? Well, that's when you start accumulating infect (poison) counters. Once your health reaches 0, for every 1 damage, you get 1 poison counter. Once you reach 10 poison counters, you lose; BUT not if Solemnity is on the field. You can't accumulate counters of any kind while that is out, including those pesking infect counters. Phyrexian Unlife + Solemnity is a wonderful way to stall the game until you can win. Just remember, once Phyrexian Unlife is removed and you have 0 life points, that's game over for you.
THE LAMBS:
Bloodghast doesn't have a death trigger, but comes back everytime a land enters the battlefield under your control. Geralf's Messenger deals deals 2 damage to your opponent each time it enters the battlefield.
Murderous Redcap deals damage (2 base power) equal to it power to any target when it enters the battlefield.
Lastly, we have Kitchen Finks. On the other end of the spectrum, you'll gain 2 life every time Kitchen Finks enters the battle field.
THE ALTARS:
Greater Gargadon is not something you're going to Cascade into. Instead, it has a suspend cost, but for 10 turns. That is a long time to wait. Most games will be over by the time you're able to actually use it... except you can lower the time counter everytime you sacrifice an artifact, creature, or a land.
Viscera Seer let's you draw anything in your deck by taking advantage of the sacrifice loop. Sacrifice a creature, Scry 1. Just sacrifice during your upkeep, then draw your card; or just sacrifice to kill your opponent. The world is your graveyard.
Phyrexian Obliterator is a big, bad bitch when the conditions are right. If you block it, you lose permanents equal to the damage your blockers dealt. If you don't block it, you take 5 to the face. Want to cast instants like Lightning Bolt to try and wipe it out? You fiddna lose a lot of yo' shit. Still, a simple Fatal Push with the revolt triggered or Terminate will wipe it out. Don't put all of your eggs in that basket. It's bark is as bad as it's bite if you give it the chance. Imagine someone using Aether Vial to flash that in as a blocker.
THE RECKONING:
Fatal Push is a staple for most decks that run black mana. Don't forget, it can destroy up to a 4 mana creature at instant speed as long as a permanant of your left the battlefield that turn. That includes your fetch lands.
Damn - when you just want to watch the world burn. Kill a creature, or kill all creatures.
Vindicate just kills anything and everything that isn't indestructible. Including lands. Speaking of indestructible...
Anguished Unmaking exiles anything that isn't a land at instant speed.
Vanishing Verse also exiles any permanant for ONLY 2 mana at instant speed, but only if it's mono-colored. You can't have everything.
You can't actually kill Indestructible creatures. They have to be taken care of in other ways like, previously mentioned, exiling them. There are other ways of killing the unkillable, like using Tragic Slip. Since Tragic Slip doesn't actually "destroy" anything, it just brings the toughness down to or past 0; which, in turn, kills it. Since all you're doing is sacrificing your creatures, which counts as the creatures dying, that is 1 mana -13/-13 at instant speed. That's fucking NUTS! To help the newer players out there understand how strong this card is, it would end up taking out Ulamog, the Ceaseless Hunger, which is considered to be a game ending threat.
Should Shambling Vent be in here? Probably not, but this is my deck and I like it. Shambling Vent and Raging Ravine have both been the sole reason I was able to win some pretty tough matches, so don't always rule manlands out. Still, you could just add another swamp or Silent Clearing for added card draw. I'd honestly be surprised if you managed to read this far into my descent into madness without rolling your eyes or just exiting out completely.
SIDEKICKS: Silence and Thoughtseize are well rounded cards that will help against most decks. Control decks are a tough match for many decks due to the seemingly unlimited amount of counterspells they have.
Thoughtseize not only let's you know what your opponent has, but also let's you dispense of the worst of the threats on the spot.
Silence literally prevents your opponent from casting any spells on whatever turn you you choose, so use that time wisely.
Considering how important your graveyard is to your gameplan, you should probably protect it. That's where Leyline of Sanctity comes in. It's not perfect, but it's better than nothing. It also prevents your opponents from using cards like Thoughtseize and Lightning Bolt on you, because it gives you hexproof.
Necromentia is perfect for sideboarding. After round one, you should have an understanding of what you are up against, so use Necromentia to get rid of the spell that will hinder you the most.
Now, I understand some people may disagree with sideboarding Altar of Dementia, but there is a good reason I chose it. The same reason why I chose Necromentia. Your opponent will know what you have and will plan on stopping you with some kind of removal or permanant freeze. Altar of Dementia is another win-con you can use by sacrificing your undying creatures.
In The End: Sacrifice Geralf's Messenger or Murderous Redcap to Greater Gargadon or Viscera Seer until your opponent dies from the damage triggers from entering the battlefield over and over or until you manage to cast Greater Gargadon and then just rinse and repeat. It's the same thing with Kitchen Finks, but you'll either have an infinite life loop with Viscera Seer or you will actually cast Greater Gargadon and have a shit ton of health. Altar of Dementia will either mill your opponent with Kitchen Finks or kill them with Geralf's Messenger and Murderous Redcap. Your creatures are fodder. Keep killing them until your opponent is dead.