Whenever a creature with power 1 or less is put into your graveyard from the battlefield, you may return that card to the battlefield at the beginning of the next end step if Shirei is still on the battlefield.
Shirei abuses creatures with power 1 or less by recurring them every end step, generating endless death triggers, sacrifice fodder, and ETB value. You flood the board with cheap utility creatures, then loop them through sacrifice outlets and aristocrat payoffs to drain the table or assemble a combo. The deck grinds out incremental advantage until your engine snowballs out of control.
Relentless recursion of cheap creatures generates inevitable card and value advantage
Excellent resilience to spot removal and board wipes since creatures keep coming back
Access to powerful infinite combos for compact, repeatable wins
Mono-black gives strong tutors, removal, and recursion support
Heavily commander-dependent; if Shirei dies the whole engine stops
Vulnerable to graveyard hate and exile-based removal
Triggers only at end step, so it can be slow and clunky without sac outlets
Low power creatures mean little defense against aggressive boards before the engine comes online
Free, repeatable sac outlet that grows and enables Shirei loops.
Add fast mana and protection for Shirei like Lightning Greaves and Swiftfoot Boots so your engine survives removal. Tighten the combo package—Pitiless Plunderer, a free sac outlet, and a drain effect for infinite loops—and include tutors like Demonic Tutor and Diabolic Intent. Round out with graveyard insurance and recursion (Reanimate, Victimize) plus efficient interaction to keep the table in check.