Reaping Willow + Phyrexian Altar + Plague Belcher + Training Grounds

Reaping Willow

Phyrexian Altar

Plague Belcher

Training Grounds

How it works

1. Activate Reaping Willow by paying W/B due to Training Grounds and removing two counters from it, returning Plague Belcher from your graveyard to the battlefield.
2. When Plague Belcher enters, it triggers, putting two -1/-1 counters on Reaping Willow.
3. Activate Phyrexian Altar by sacrificing Plague Belcher, adding W/B.
4. Repeat.

This engine turns Reaping Willow into a recycling plant by using Training Grounds to slash its resurrection cost down to a single {W/B} mana. When you sacrifice Plague Belcher to Phyrexian Altar for that necessary mana, Plague Belcher heads to the graveyard while fueling your death and sacrifice triggers. Bringing it back with Reaping Willow's ability triggers Plague Belcher's enter-the-battlefield effect, neatly sliding two new -1/-1 counters right back onto Reaping Willow so its removal ability can be activated all over again.