Mortuary + Phyrexian Dreadnought + Gwenom, Remorseless + Sifa Grent

Mortuary

Phyrexian Dreadnought

Gwenom, Remorseless

Sifa Grent

How it works

1. Cast Phyrexian Dreadnought from the top of your library by paying 1 life.
2. When Phyrexian Dreadnought enters, it triggers, causing you to sacrifice it.
3. When Phyrexian Dreadnought dies, Mortuary and Sifa Grent trigger.
4. Resolve the Mortuary trigger, putting Phyrexian Dreadnought from your graveyard onto the top of your library.
5. Resolve the Sifa Grent trigger, causing you to gain 1 life and target opponent to lose 1 life.
6. Repeat.

This clever loop hinges on Gwenom, Remorseless, whose attack trigger lets you cast creature spells directly from the top of your library by paying life equal to their mana value instead of their mana cost. You use this ability to cast Phyrexian Dreadnought for a single life, bypassing its massive power requirement for sacrifice. As soon as the Dreadnought hits the battlefield, its enters-the-battlefield trigger forces you to sacrifice it immediately. That trip to the graveyard triggers Mortuary, which instantly recycles Phyrexian Dreadnought right back onto the top of your library so Gwenom can play it again. Meanwhile, Sifa Grent watches the carnage unfold, draining your opponent's life total and padding your own life buffer with every single sacrifice loop.