If Volibear, Relentless Storm triggers when a Mighty unit is played, but the opponent uses Stupefy to reduce the unit's power below 6 before Volibear's ability resolves, does Volibear still channel a rune?

Ruling: You still get the rune. The Mighty requirement is checked in the trigger condition when the unit is played, not upon resolution.

Nuances:

• The resolution text only says "you may exhaust me to channel 1 exhausted" because the Mighty requirement is already satisfied in the trigger condition
• Reducing the unit's power after it triggers Volibear's ability does not prevent the ability from resolving