When Michelangelo dies, it and Deathrender trigger.
Resolve the Michelangelo trigger, returning it from your graveyard to your hand.
Resolve the Deathrender trigger, putting Michelangelo from your hand onto the battlefield and attaching Deathrender to it.
Resolve the Shilgengar ability.
Repeat.
This clever loop turns Michelangelo, On the Scene into a self-sustaining sacrifice engine with the help of Shilgengar, Sire of Famine, which converts each iteration into a flood of Blood tokens by taking advantage of Michelangelo's death trigger returning it straight to your hand. Meanwhile, Deathrender acts as the crucial bridge that bypasses the hand entirely, letting you immediately drop Michelangelo back onto the battlefield and reattaching itself to keep the cycle going without missing a beat.