Hellkite Charger, and Bear Umbra

Prerequisites

• Hellkite Charger on the battlefield
• Bear Umbra on the battlefield
• Hellkite Charger does not have summoning sickness
• Bear Umbra attached to Hellkite Charger
• You control lands that can tap to produce at least
• An opponent is unable to block and kill Hellkite Charger

Steps

1. Declare Hellkite Charger as attacker
2. Bear Umbra and Hellkite Charger triggers
3. Resolve the Bear Umbra's trigger, untapping all lands you control
4. Resolve the Hellkite Charger's trigger, choosing to pay to untap all attacking creatures and to get an additional combat phase after this one
5. Repeat

Results

• Infinite combat phases