Keiga, the Tide Star + Nim Deathmantle + Pitiless Plunderer + Phyrexian Altar

Keiga, the Tide Star

Nim Deathmantle

Pitiless Plunderer

Phyrexian Altar

How it works

1. Whenever an opponent controls a creature, activate Phyrexian Altar by sacrificing Keiga, adding 1.
2. When Keiga dies, it, Pitiless Plunderer and Nim Deathmantle trigger.
3. Resolve the Pitiless Plunderer trigger, creating a Treasure artifact token.
4. Resolve the Keiga trigger, causing you to gain control of a creature an opponent controls.
5. Activate Phyrexian Altar by sacrificing the creature you gained control of in step 3, adding 1.
6. When the creature dies, Pitiless Plunderer triggers, creating a Treasure artifact token.
7. Activate the Treasures by tapping and sacrificing them, adding 2.
8. Resolve the Nim Deathmantle trigger from step 2, causing you to pay 4 to return Keiga from your graveyard to the battlefield, and attach Nim Deathmantle to it.
9. Repeat as desired and/or whenever a creature enters the battlefield under an opponent's control.

This devious loop turns your opponents' own creatures against them while cleanly recycling your own threats. By sacrificing Keiga, the Tide Star to Phyrexian Altar, you trigger both Pitiless Plunderer and Nim Deathmantle, which happily provides the mana and the recursive resurrection engine to bring Keiga right back. Meanwhile, Keiga's own death trigger lets you permanently steal an opposing creature, which you can then sacrifice to the Altar to generate the extra mana needed to fund Nim Deathmantle's hefty {4} revival cost.