Prowling Geistcatcher + Phyrexian Delver + Gray Merchant of Asphodel + Phantom Train

Prowling Geistcatcher

Phyrexian Delver

Gray Merchant of Asphodel

Phantom Train

How it works

1. Activate Phantom Train twice by sacrificing Phyrexian Delver and Gray Merchant.
2. When Phyrexian Delver and Gray Merchant die, Prowling Geistcatcher's first ability triggers twice, exiling Phyrexian Delver and Gray Merchant from your graveyard.
3. Activate Phantom Train by sacrificing Prowling Geistcatcher.
4. When Prowling Geistcatcher dies, its second ability triggers, returning Phyrexian Delver and Gray Merchant from exile to the battlefield.
5. When Phyrexian Delver and Gray Merchant enter the battlefield, they trigger.
6. Resolve the Gray Merchant trigger, causing each opponent to lose an amount of life equal to your devotion to black, and causing you to gain life equal to the life lost this way.
7. Resolve the Phyrexian Delver trigger, causing you to return Prowling Geistcatcher from your graveyard to the battlefield and lose 4 life.
8. Resolve the Phantom Train abilities from steps 1 and 3.
9. Repeat.

This loop transforms Phantom Train into a lethal engine by using its activation cost to feed our sacrifice triggers, with Prowling Geistcatcher acting as the ultimate holding cell that keeps our pieces safe in exile. By sacrificing Phyrexian Delver and Gray Merchant of Asphodel to the Train, we prime the Geistcatcher to swallow them up rather than letting them rest in the graveyard; then, sacrificing Prowling Geistcatcher itself flushes everything back onto the battlefield at once. This instantly triggers Gray Merchant of Asphodel to drain our opponents dry while Phyrexian Delver fishes the Geistcatcher right back out of the graveyard to repeat the cycle infinitely.