Moonfall

Q: My opponent plays Moonfall targeting my unit and a battlefield where they have a Travelling Merchant on, and the Merchant is the only unit they control on that battlefield. If I Gust the Merchant in response to Moonfall, does my unit still move and receive -2 at the battlefield?

A: No, the unit won’t move and no -2M will be given.

“Where you have units” is a targeting requirement for the chosen battlefield. Upon resolving, if that requirement is not met, the spell will check information about an illegal target, so “that battlefield” and “there” will return null, and the related instructions will be ignored.

Relevant rules:

• 359.3.e.2. A target is illegal as the spell resolves if it no longer meets the targeting requirements of the spell, or if it has changed Zones to or from a Non-Board Zone.
• 359.3.e.6. Instructions that can't be followed, either because of illegal targets or other circumstances, are ignored.
• 359.3.e.12. If the spell checks information about a target that is no longer legal or a card or permanent whose location, zone, or status has changed such that that information is no longer available, that check returns "null" and all calculations based on it are ignored