Infinite $15 Sacrifice deck (Modern)

Get Tenacious Dead or Reassembling Skeleton into play.

Add Zulaport Cutthroat or Blood artist.

Use Viscera Seer or Defiant Salvager to sacrifice your Tenacious Dead or Reassembling Skeleton.

Add either 2 Pitiless Plunderer or one Pitiless Plunderer and an Open the Graves. When your sacrifice fodder dies, you will get either 2 mana or a mana and a token which you can sacrifice for another mana. Use the mana to bring your sacrifice fodder back to repeat.

This is a great starting point for this deck. Your first upgrade would be 3 more Viscera Seer. With more money Gravecrawler and Nether Traitor are good alternatives for Reassembling Skeleton and Tenacious Dead. Dark Petition or Harvester of Souls is also a great add to make drawing your combo more consistent. As this deck can get mana heavy, consider Pristine Talisman or Leaden Myr. It would also be a good fit for a combo with a green mana ramp deck.

This deck requires 5 cards on the field for the combo to work, so draw power is your number one goal with improvements.

Other win conditions are attacking directly with a pumped up Defiant Salvager. You can also chip away at their life total each turn with all aspects of the combo except for the mana. Defensively, this deck is good against a deck that depends on attacking to win. Blocking with sacrificial fodder while you have a Blood Artist or Zulaport Cutthroat is very frustrating for the attacker. This deck is poor against mill decks since it is so slow. Any deck with heavy spot removal, like a red deck, will shut down your combo, so consider a side board with cards that return creature cards from the graveyard.