This clever loop revolves around Shilgengar, Sire of Famine's sacrifice ability, which normally costs you creatures to generate Blood tokens. By feeding Rendclaw Trow to the Sire, you immediately trigger the Trow's persist ability to bring itself right back from the graveyard. Normally, the -1/-1 counter from persist would eventually shut the loop down, but Vizier of Remedies steps in to cleanly reduce that counter placement to zero. This allows Rendclaw Trow to keep dying endlessly, letting Shilgengar, Sire of Famine churn out infinite Blood tokens and artifact tokens while triggering endless entry, leaving, and death effects.