Infinite creature LTBInfinite creature ETBInfinite creature sacrifice triggersInfinite death triggersInfinite colorless manaInfinite mana creatures you control can produceInfinite untap of creatures
How it works
Activate Xu-Ifit by tapping it, returning a creature card from your graveyard to the battlefield.
When the creature enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Activate Ashnod's Altar by sacrificing the creature returned in step 1.
Repeat.
This loop turns Xu-Ifit, Osteoharmonist into an endless engine of resurrection by exploiting the constant influx of new arrivals. Whenever Xu-Ifit taps to return a creature card from your graveyard to the battlefield stripped of its text, that new entry triggers Intruder Alarm to immediately untap all creatures—including Xu-Ifit itself. You can then feed that resurrected creature to Ashnod's Altar to generate a steady stream of colorless mana, which also leaves your board clear to repeat the entire cycle anew.