Chainer, Dementia Master + K'rrik, Son of Yawgmoth + Gray Merchant of Asphodel + Phantom Train
Chainer, Dementia Master
K'rrik, Son of Yawgmoth
Gray Merchant of Asphodel
Phantom Train
Infinite +1/+1 counters on a creatureInfinite creature ETBInfinite creature LTBInfinite death triggersInfinite lifegainInfinite lifegain triggersInfinite lifelossInfinite creature sacrifice triggersReturn all creature cards from all graveyards to the battlefield under your control
How it works
Activate Phantom Train by sacrificing Gray Merchant.
Activate Chainer by paying 9 life due to K'rrik, returning Gray Merchant from your graveyard to the battlefield as a Nightmare in addition to its other creature types.
When Gray Merchant enters, it triggers, causing each opponent to lose life equal to your devotion to black and causing you to gain that much life.