Combine Guildmage, and Phantom Train

Prerequisites

• Combine Guildmage on the battlefield
• Phantom Train on the battlefield
• available

Steps

1. Activate Combine Guildmage's first ability by paying and tapping it
2. Activate Phantom Train by sacrificing the persist creature
3. When the persist creature dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Combine Guildmage
4. Resolve the Phantom Train ability
5. Repeat from step 2

Results

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