When a unit with a move trigger (like Wandering Merchant) moves to a contested battlefield, can you play a spell drawn from that trigger before showdown/combat begins and before the defender's abilities (like Stalwart Poro's shield) activate?

Ruling: No, there is no opportunity to play a spell drawn from the move trigger before showdown begins and the defender gets their shield. Once the move trigger resolves and the chain is empty (with no additional triggers), showdown begins immediately without priority passing.

Sequence:

• Move trigger (like Wandering Merchant) activates and resolves
• If no additional triggers are created, the game transitions from closed to open state
• Showdown begins immediately without players passing priority on an empty chain
• Defender's abilities (like Stalwart Poro's shield) activate during showdown

Nuances:

• If the move trigger causes additional triggers (like discarding Scrap Heap which has its own trigger), you could play a spell as a reaction to that secondary trigger before showdown begins
• However, if you draw the spell from the secondary trigger itself, you're back in the same situation with no opportunity to play it before showdown
• Some spells (like Cannon Barrage) require combat to have already started, so they couldn't be played before showdown anyway