Altar of Dementia by sacrificing the creature with power of 3 or greater.
When the creature dies,
Pitiless Plunderer triggers, creating a Treasure artifact token.
Resolve the
Altar of Dementia ability, causing you to mill cards equal to the creature's power.
Activate the Treasure by tapping and sacrificing it, adding one mana of any color.
Cast the creature from your graveyard by paying its mana cost plus exiling three other cards from your graveyard.
Repeat.
Notes
Depending on which creature you choose, there may be additional requirements. For example, Death's Shadow would require your life total to be 10 or less. There may also be additional results (generally unfavorable ones). If the creature has a problematic ETB ability, do not resolve the ability until the creature has been sacrificed.