This clever loop relies on Squee, the Immortal's uncanny ability to repeatedly cast itself straight out of the graveyard, feeding Ashnod's Altar for a steady supply of colorless mana. Every time Squee hits the stack from anywhere other than your hand, The Thirteenth Doctor's Paradox ability triggers to place a +1/+1 counter on Crystalline Crawler. Thanks to Pir, Imaginative Rascal's replacement effect, that counter generation is amplified, dropping even more fuel onto Crystalline Crawler that you can immediately tap into for colored mana by removing them. While Team TARDIS is technically along for the ride to untap your modified creatures during the end step, the core engine runs entirely on casting Squee, sacrificing it, and siphoning the resulting resources through Crystalline Crawler's counters and Ashnod's Altar.