Activate a Treasure by tapping and sacrificing it, adding .
Krenko triggers, causing you to pay to create a 1/1 Goblin creature token with haste.
Activate Phyrexian Altar by sacrificing the Goblin token, adding one mana of any color.
When the Goblin dies, Pitiless Plunderer triggers, creating a Treasure token.
Repeat.
This delightful engine uses Phyrexian Altar as a reliable sacrifice outlet to continuously feed the loop, turning every iteration into raw profit. When you sacrifice your creature, Pitiless Plunderer steps in to generate a fresh Treasure token, replacing your lost material with a shiny new artifact. You can then crack that Treasure for mana, which Krenko, Baron of Tin Street eagerly watches for; Krenko's triggered ability lets you pay that red mana to immediately spawn a replacement 1/1 Goblin token with haste, restarting the whole cycle with endless potential.