K'rrik (Doomsday Combo)

The Decklist:

This is what I consider to be the strongest version of the deck, though cheaper variants can still be quite competitive. This deck is entirely based on resolving Doomsday and winning the game with the cards in the pile. 

                                                                                                                                                                   

Early Game Strategy

The deck utilizes early ramp and card draw in order to play K'rrik and find Doomsday as early as possible. It also has a significant tutor density.

Ramp

The deck also runs a significant artifact ramp package that can be seen in the list above. Once K'rrik is out, Blood Celebrant becomes one of the best cards in the deck as it can fill generic costs K'rrik can't pay.

Card Draw

The deck also runs a large package of 1 drop black cards that either draw 1 or cycle to draw one. Once K'rrik is out Villis can draw cards very quickly, though that isn't a primary route on account of the high cmc for Villis.

Tutors

   

The Combos

Once K'rrik is out and you have doomsday (and hopefully a draw spell) in hand you can win with any of the following lines of play.

-------------------- Mike/Trike Pile --------------------
- Ransack the Lab
- Mikaeus, the Unhallowed (Mike)
- Triskelion (Trike)
- Victimize

Lowest Life/Board Requirements: 17 life, K'rrik out, 3 Colorless

1. Cast Doomsday - 11 life
2. Doomsday resolves - 5 life
3. Cast Ransack to pitch Mike/Trike and keep Victimize - 3 life
4. Cast Victimize, sacrificing K'rrik to bring back Mike/Trike - 1 life
5. Executing the Loop: Ping 2 with Trike, Trike kills itself, it comes back off Mikaeus with 4 counters, ping 3, kill itself. Repeat to kill the table.

-------------------- Bontu/Ball Pile --------------------
- God-Eternal Bontu
- Sacrifice
- Mikaeus, the Unhallowed (Mike)
- Carrion Feeder
- Walking Ballista (Ball)

Lowest Life/Board Requirements: 20 life, K'rrik out, 3 Colorless

1. Cast Doomsday - 14 life
2. Doomsday resolves - 7 life
3. Cast Bontu - 3 life
4. Cast Sacrifice, sacrificing K'rrik, net {BBBBBBB} - 1 life
5. Cast Mikaeus the Unhallowed
6. Cast Carrion Feeder
7. Cast Walking Ballista
8. Executing the Loop: Sac Ballista to Feeder, Ballista comes back off Mikaeus with 1 counter, ping 1, sac Ballista. Repeat to kill the table.

--------------------- Zuran/Sigil Pile ---------------------
- Bolas's Citadel
- Zuran Orb
- Aetherflux Reservoir
- 0-CMC spell
- Leshrac's Sigil

Lowest Life/Board Requirements: 28 life, K'rrik out, 3 Colorless

1. Cast Doomsday - 22 life
2. Doomsday resolves - 11 life
3. Use {3} to cast Citadel - 5 life
4. Cast Zuran Orb - 5 life
5. Cast Aetherflux - 5 life
6. Cast 0-drop - 8 life
7. Cast Leshrac's Sigil - 11 life
8. Executing the Loop: Return Sigil to hand (lose 4, go to 7), cast Sigil (lose 4, gain 7, go to 13). Repeat for infinite life and kill the table with Aetherflux.
Zuran Orb can also be used to gain more life to protect yourself by sacrificing lands. Your 0-drop can also be Mox Opal to save 2 life.

------------------- Carrion/Crawler Pile -------------------
- Bolas's Citadel
- Aetherflux Reservoir
- 0-drop
- Carrion Feeder
- Gravecrawler

Lowest Life/Board Requirements: 30 life, K'rrik out, 3 Colorless

1. Cast Doomsday - 22 life
2. Doomsday resolves - 11 life
3. Use {3} to cast Citadel - 5 life
4. Cast Aetherflux Reservoir - 1 life
5. Cast 0-drop - 5 life
6. Cast Carrion Feeder - 9 life
7. Cast Gravecrawler - 14 life
8. Executing the Loop: Sac Crawler to Feeder, play Feeder from grave for 2 life, net positive life off Aetherflux. Repeat for infinite life and kill the table with Aetherflux.

-------------------- Mortuary/Gary Pile --------------------
- Bolas's Citadel
- Gray Merchant of Asphodel (Gary)
- Mortuary
- Carrion Feeder / Viscera Seer

Lowest Life/Board Requirements: 30 life, K'rrik out, {3}

1. Cast Doomsday - 24 life
2. Doomsday resolves - 12 life
3. Use {3} to cast Citadel - 6 life
4. Cast Gray Merchant of Asphodel - 28 life (draining the table of 9 life per player, gaining 27)
5. Cast Mortuary - 24 life
6. Cast Carrion Feeder - 23 life
7. Executing the Loop: Sac Gary to Feeder, Mortuary puts Gary on top, cast Gary (losing 5, drain 11 from each, gain 33) to net +28 life. Repeat to kill the table with Gary ETBs.
At 28 Life: B = Black mana S = Storm Count L = Life C = Colorless Mana 

You already casted K'rrik -> 1S Tap 3 lands -> 3C (using colorless just in case you don't have all swamps out) Cast Doomsday -> Pay 6 down to 22, then it gets halved, down to 11L 2S Cast DRAW SPELL HERE FROM HAND (use a rock or something? idk?) -> 11L 3S Cast Bolas Citadel using the 3 -> 5L 4S Cast Zuran Orb -> 5L 5S Cast Aetherflux -> 5-4 = 1L 6S Cast 0 Drop -> 1 + 7(Storm) = 8L 7S Cast Sigil -> 8 - 4(cast) + 8(Storm) = 12 (Primer says 11) Bouncing and Casting Sigil costs 8 life per loop. You're generating 8+ life per loop now. It's infinite