Maester Seymour, Crystalline Crawler, and Najeela, the Blade-Blossom

Prerequisites

• Maester Seymour on the battlefield
• Crystalline Crawler on the battlefield
• Najeela, the Blade-Blossom on the battlefield

Steps

1. At the beginning of your combat phase, Maester Seymour triggers, putting at least five +1/+1 counters on Crystalline Crawler
2. Activate Crystalline Crawler's first ability five times by removing five +1/+1 counters from it, adding
3. Activate Najeela by paying , untapping all attacking creatures you control and causing you to get an additional combat phase after this one
4. Repeat

Results

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