https://tappedout.net/mtg-decks/krrik-citadel-cedh-primer/
https://tappedout.net/mtg-decks/krrik-cedh-primer/
https://www.mtggoldfish.com/articles/budget-commander-k-rrik-son-of-yawgmoth-50-100-200
https://tappedout.net/mtg-decks/krrik-cedh/
https://www.moxfield.com/decks/ksOWqeElwUaNmAeybXoEjw/primer

Chainer Combo
Have the following on the battlefield
1) Chainer, Dementia Master
2) K'rrik, Son of Yawgmoth
3) Viscera Seer
4) Gray Merchant of Asphodel
Sacrifice Gray Merchant of Asphodel to vescera seer then activate chainer,dementia master this will cost 9 life reanimate Gray Merchant of Asphodel and when Gary enters opponents will lose 8 life each and you will gain 24 life meaning you net gain 16 per activation.

The math
It will cost us 8 life for each cast and return. Once we're able to cast this spell and gain 8 life per cast we have a combo. The absolute minimum amount of life we can start this loop with just K'rrik, Son of Yawgmoth + Aetherflux Reservoir + Leshrac's Sigil is 37.
37-8+1=30
30-8+2=24
24-8+3=19
19-8+4=15
15-8+5=12
12-8+6=10
10-8+7=9
9-8+8=9

Lifedrain "Storm." Chain together a bunch of spells together with an extort card like Pontiff of Blight out or Aetherflux Reservoir, or finish with a huge Tendrils of Agony.

K'rrik, Son of Yawgmoth + Aetherflux Reservoir + Leshrac's Sigil
K'rrik, Son of Yawgmoth + Aetherflux Reservoir + Gravecrawler + Carrion Feeder
K'rrik, Son of Yawgmoth + Aetherflux Reservoir + Carrion Feeder + Liliana, Untouched by Death
K'rrik, Son of Yawgmoth + Bolas's Citadel + Gray Merchant of Asphodel + any sac outlet + Mortuary