Mortuary + Sling-Gang Lieutenant + Aetherflux Reservoir + Gwenom, Remorseless

Mortuary

Sling-Gang Lieutenant

Aetherflux Reservoir

Gwenom, Remorseless

How it works

1. Cast Sling-Gang Lieutenant either from the top of your library by paying 4 life or from your hand by paying 3.
2. Aetherflux Reservoir triggers, causing you to gain 1 life for each spell you've cast this turn.
3. When Sling-Gang Lieutenant enters, it triggers, creating two 1/1 Goblin creature tokens.
4. Activate Sling-Gang Lieutenant three times by sacrificing the Goblin tokens and then Sling-Gang Lieutenant.
5. When Sling-Gang Lieutenant dies, Mortuary triggers, putting Sling-Gang Lieutenant from your graveyard onto the top of your library.
6. Resolve all Sling-Gang Lieutenant abilities, causing target opponent to lose 3 life and you to gain 3 life.
7. Repeat.

This loop is elegantly fueled by Gwenom, Remorseless, whose attack trigger lets you bypass traditional mana costs by paying life to cast creatures from the top of your library instead. You deploy Sling-Gang Lieutenant, and as its entrance fills your board with two Goblin creature tokens, Aetherflux Reservoir steadily inflates your life total with every spell you cast to help sustain Gwenom's life-payment costs. You then sacrifice those tokens along with the Lieutenant itself to fuel the Lieutenant's own drain ability, which triggers Mortuary to seamlessly place the Lieutenant right back onto the top of your library for Gwenom to play again.