Imperious Perfect + Faces of the Past + Ashnod's Altar + Llanowar Elves

Imperious Perfect taps for one mana from Llanowar Elves to mint an Elf Warrior token, Ashnod's Altar sacrifices it for two colorless, and Faces of the Past untaps every Elf and Warrior when the token dies — netting one colorless per loop with Llanowar Elves refreshing the green for the next activation. The loop is native to any Elf tribal commander in green-blue, where Imperious Perfect and Llanowar Elves are already core pieces and Ashnod's Altar is a standard sacrifice outlet. Faces of the Past is the narrow dependency here — it lives only in blue, pulls no synergy weight outside this line, and dies to enchantment removal before the loop even assembles.