Siege Dragon attacks in a 2HG game. In what conditions does it trigger? What choices if any are made when it's put on the stack? What happens as it resolves?

Edited Jan Grottel (July 13, 2014 11:19:32 AM)

It's an “intervening if” trigger, which means that you check the condition both at triggering time and at resolution.

As the trigger refers to “defending player”, the attacking team chooses one opponent to be the defending player (for this trigger) as it triggers. It's then put onto the stack if the condition is met. At resolution, you check the condition again and apply the effect if it's met - with the same defending player.

Daniel Kitachewsky
L4, Paris, France
Rules NetRep

My previous answer was incorrect, apologies!

The trigger condition and the trigger's effect are treated differently.

The condition is met if neither defending player controls any Walls. If any of them controls a Wall, it will not trigger. If neither controls any Walls on resolution, then you have a one-shot effect to apply referring to defending player, and that's the point where you choose one of the two players to be affected.

Daniel Kitachewsky
L4, Paris, France
Rules NetRep