If an opponent plays Cull the Weak targeting my only unit, can I respond with Gust to return that unit to my hand, and what happens to Cull the Weak if I have no other units?

Ruling: Yes, you can play Gust in response to move your unit back to your hand. If you have no units remaining in play after Gust resolves, your opponent must still sacrifice one of their own units to fulfill Cull the Weak's requirement.

Sequence:

• Opponent plays Cull the Weak
• You respond with Gust, returning your only unit to hand
• Gust resolves first
• Cull the Weak resolves, but you have no units
• Opponent must sacrifice one of their own units