Can Shen be played to a contested battlefield (Gods Willow) using his Reaction ability when the opponent moves a unit there, even though the opponent doesn't control that battlefield?

Ruling: No, this is not legal. You can only play units to battlefields you control, and Shen's opponent does not control Gods Willow in this scenario.

Nuances:

• The Reaction keyword rules contain the restriction that units can only be played to battlefields you control
• Shen's reminder text also mentions this restriction, though reminder text itself has no effect on game function
• The hypothetical scoring sequence question becomes moot since the play is illegal