Zellix, Sanity Flayer, Haunted One, Pith Driller, Ashnod's Altar, and Intruder Alarm

Prerequisites

• Zellix, Sanity Flayer on the battlefield
• Haunted One on the battlefield
• Pith Driller on the battlefield
• Ashnod's Altar on the battlefield
• Intruder Alarm on the battlefield
• Zellix does not have summoning sickness
• Pith Driller does not have a +1/+1 counter on it
• available

Steps

1. Activate Zellix by paying and tapping it
2. Haunted One triggers, causing all Horrors you control to get +2/+0 and undying until end of turn
3. Resolve the Zellix ability, causing a player to mill three cards
4. If the player milled a creature card this way, Zellix triggers, creating a 1/1 Horror creature token
5. Activate Ashnod's Altar by sacrificing Pith Driller, adding
6. When Pith Driller dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
7. When Pith Driller enters the battlefield, it and Intruder Alarm trigger
8. Resolve the Pith Driller trigger, putting a -1/-1 counter on it
9. Resolve the Intruder Alarm trigger, untapping all creatures
10. Repeat

Results

• Infinite colorless mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinitely powerful Horrors you control until end of turn except Pith Driller
• Infinite mana creatures you control can produce
• Infinite mill
• Infinite sacrifice triggers
• Infinite self-mill
• Infinite untap of all creatures
• Near-infinite creature tokens
• Near-infinite LTB
• Near-infinite death triggers
• Near-infinite sacrifice triggers
• Near-infinite colorless mana