Watchful Radstag, Master Biomancer, and Tyranid Prime

Prerequisites

• Watchful Radstag on the battlefield
• Master Biomancer on the battlefield
• Tyranid Prime in hand
• available

Steps

1. Cast Tyranid Prime by paying
2. When it enters, Watchful Radstag's evolve ability triggers, putting a +1/+1 counter on it
3. Its second ability triggers, creating a token copy of it that enters with a number of +1/+1 counters equal to Master Biomancer's power
4. When the token enters, each creature you control's evolve ability will trigger if the token has lesser toughness or power
5. Resolve all evolve triggers except those from Watchful Radstags, putting a +1/+1 counter on each of them
6. Resolve a Watchful Radstag trigger, putting a +1/+1 counter on it
7. Its second ability triggers, creating a token copy of it that enters with a number of +1/+1 counters equal to Master Biomancer's power
8. Repeat from step 3

Results

• Infinite ETB
• Infinite +1/+1 counters
• Infinite +1/+1 counters on an infinite number of creature tokens