Maester Seymour, Crystalline Crawler, and Hellkite Charger

Prerequisites

• Maester Seymour on the battlefield
• Crystalline Crawler on the battlefield
• Hellkite Charger on the battlefield

Steps

1. At the beginning of your combat phase, Maester Seymour triggers, putting at least seven +1/+1 counters on Crystalline Crawler
2. Declare Hellkite Charger as an attacker, triggering its ability
3. Holding priority, activate Crystalline Crawler's first ability seven times by removing seven +1/+1 counters from it, adding
4. Resolve the Hellkite Charger trigger, causing you to pay to untap all attacking creatures you control and to get an additional combat phase after this one
5. Repeat

Results

• Infinite colored mana
• Infinite combat phases
• Infinite +1/+1 counters