If Darius is reduced to 0 health by Void Seeker, then the opponent uses an action and reaction during combat, and I play Stupefy in response, does Darius die before his ability resolves or does he get +2/+2 first?

Ruling: If Stupefy resolves before Darius's action, then Darius dies before getting the +2/+2 buff.

Sequence:

• Void Seeker resolves, reducing Darius to 0 health
• During combat, opponent uses action and reaction
• You play Stupefy in response
• If Stupefy resolves first, it counters the action
• Darius dies before the +2/+2 can apply

Nuances:

• The key is whether Stupefy resolves before Darius's action resolves on the stack