Tainted Observer + Ashnod's Altar + Herd Baloth

Prerequisites

• You have a way to cause a creature to enter the battlefield under your control.
• Herd Baloth has at least one +1/+1 counter on it.

Steps

1. 1Cause a creature to enter the battlefield under your control.
2. 2When the creature enters the battlefield, Tainted Observer triggers.
3. 3Holding priority, activate Ashnod's Altar by sacrificing the creature, adding .
4. 4Resolve the Tainted Observer trigger, causing you to pay to put a +1/+1 counter on Herd Baloth.
5. 5Herd Baloth triggers, creating a 4/4 Beast creature token.
6. 6Repeat from step 2.

Effects

• Infinite +1/+1 counters on a creature
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers
• Infinite proliferate