Splinter Twin, Cinderhaze Wretch, and Cathars' Crusade

Prerequisites

• Splinter Twin on the battlefield
• Cinderhaze Wretch on the battlefield
• Cathars' Crusade on the battlefield
• Splinter Twin attached to Cinderhaze Wretch
• Cinderhaze Wretch does not have summoning sickness

Steps

1. Activate Cinderhaze Wretch by tapping it, creating a token copy of it with haste
2. When the Cinderhaze Wretch token enters the battlefield, Cathars' Crusade triggers, putting a +1/+1 counter on each creature you control
3. Activate the nontoken Cinderhaze Wretch's second ability by putting a -1/-1 counter on it, untapping it
4. Repeat

Results

• Infinite creature tokens with haste
• Infinite ETB
• Infinite +1/+1 counters