Pitiless Plunderer | Phantom Train | Persistent Specimen

(and one other card)

Activate
Phantom Train by sacrificing
Persistent Specimen.
When
Persistent Specimen dies,
Pitiless Plunderer and
Skittering Precursor trigger.
Resolve the
Pitiless Plunderer trigger, creating a Treasure token.
Resolve the
Skittering Precursor trigger, creating a creature token.
Resolve the
Phantom Train ability.
Activate the Treasure by tapping and sacrificing it, adding ({B} magic symbol) .
Activate the creature token by sacrificing it, adding ({C} magic symbol) .
When the creature token dies,
Pitiless Plunderer triggers, creating a Treasure token.
Activate the Treasure by tapping and sacrificing it, adding ({1} magic symbol) .
Activate
Persistent Specimen by paying ({2} magic symbol) ({B} magic symbol) , returning it to the battlefield from your graveyard.
Repeat.

Once you have infinite Treasure tokens, you may repeat this loop spending mana from Treasures instead of Eldrazi Spawns in step 7, giving you infinite Eldrazi Spawn tokens.