The Thirteenth Doctor + Squee, the Immortal + Crystalline Crawler + Phyrexian Altar + Hardened Scales

The Thirteenth Doctor

Squee, the Immortal

Crystalline Crawler

Phyrexian Altar

Hardened Scales

How it works

1. Activate Phyrexian Altar by sacrificing Squee, adding .
2. Cast Squee from your graveyard by paying 1.
3. The Thirteenth Doctor's first ability triggers, putting two +1/+1 counters on Crystalline Crawler.
4. Activate Crystalline Crawler's first ability twice by removing two +1/+1 counters from it, adding 1.
5. Repeat.

This clever loop turns Squee, the Immortal into an endlessly recurring sacrifice engine by letting you repeatedly cast him straight from your graveyard after feeding him to Phyrexian Altar. While Squee provides the fuel, The Thirteenth Doctor keeps the machinery humming; whenever you cast a spell from anywhere other than your hand, her paradox ability triggers to distribute counters. Crystalline Crawler acts as our mana transformer, converting those incoming counters back into the colored mana we need to recast Squee, all while Hardened Scales accelerates the process by outputting extra +1/+1 counters on the Crawler every time the Doctor's trigger resolves.