This loop sets up a clever perpetual engine by exploiting how replacement and prevention effects interact with death triggers. When you feed Unstoppable Slasher to Thermopod's sacrifice ability for red mana, the Slasher tries to return with stun counters, but Solemnity steps in to prevent those counters from ever being placed. Because the creature returns completely clean of counters, it can be sacrificed over and over again to generate infinite red mana, death triggers, and leave-the-battlefield or enter-the-battlefield events.