My inspiration when creating this deck was to harness the destructive properties of one of the greatest cards of all-time, Pestilence!
I was also heavily inspired by the deck linked below created by user "Colinwc0", which was pretty out of date by today's standards. So big thanks to that guy for doing a lot of the leg work for the core of this deck.
https://www.mtgvault.com/colinwc0/decks/best-pestilence-deck/
As is, this is not a budget deck by any means, but if you cut out the dual lands, and go for cheaper tutors, the deck becomes very affordable. I have actually been running this without dual lands, and cheaper tutors, such as Beseech the Queen, and have had great results at my local shops, and on Magic Online.
The ultimate goal of this deck is to get pestilence, and either Exquisite Blood, or Urza's Armor out on the board. Since Pestilence triggers for 1 damage per pop, either of these cards will completely negate all Pestilence damage to you. Even better, is to get Pestilence and Stuffy Doll out, so you can do double damage with Pestilence.
Here is run down of why most of the cards are in here:
Swans of Bryn Argoll - These guys prevent pestilence damage to themselves, and allow you to draw for each time you pop pestilence.
Reliquary Tower - You will be drawing a lot with the Swans, so stacking a large hand is in your favor.
Words of Worship - Can basically turn each Pestilence crank into 5 life with Swans on the board. Crank Pestilence 4 times, you gain 20 life if you choose, or you could gain 5 life and draw 3 cards. It's up to you.
Stuffy Doll - He basically makes every pop of Pestilence do double damage, since you redirect damage from him, to your opponent. Ten pestilence cranks and it's game over.
Nomads en-Kor - These guys are VITAL to the deck. They allow you to redirect damage to another creature, so you have the choice to direct to Stuffy Doll and do TRIPLE damage, or your Swans, and draw extra cards. Or split the damage between both, to draw extra cards, and do extra damage. By cranking pestilence a measly 4 times, you can do 4 direct damage to your opponent, then Stuffy Doll will do 4 more damage, and Nomads, directed to Stuffy, directed to you opponent, is another 4 damage. So 12 damage for 4 mana!
Death Pits of Rath - This makes it so each crank of Pestilence destroys any of your opponents creatures. If you can clear the board, the Swans can swing in for 4 damage.
Pestilence Demon - He's there as a backup Pestilence, in case your opponent is running enchantment removal.
Elixir of Immortality - You last saving grace in the rare chance you can't something on the board to negate Pestilence. Also here just in case you might get put in a position where you might deck yourself, or to prolong the game if you are playing against an aggressive weenie deck.
Lake of the Dead - Sacrifice 5 Swamps, and it's game over.
The rest of the cards are self explanatory. Lots of mana ramp, deck searching, and protection.