If I react during a combat showdown with my hidden Guards! spell, does the Sand Soldier token get Weaponmaster from Azir's Emperor of the Sands legend? Can the Sand Soldier immediately equip equipment during the combat showdown as one reaction?

Ruling: Yes. When you play Guards! as a reaction during combat, the Sand Soldier token gains Weaponmaster from Emperor of the Sands and can immediately equip an Equipment you control before combat damage is calculated.

Sequence:

• Play Guards! as a [Reaction] during the combat showdown (it enters the chain)
• Guards! resolves, and you "play" the Sand Soldier token at that battlefield
• The Sand Soldier gains Weaponmaster from Emperor of the Sands
• Weaponmaster triggers as a "When you play me" ability and goes on the chain
• Resolve the Weaponmaster trigger to attach an Equipment you control to the Sand Soldier (paying its Equip cost, potentially at a discount)
• The equipped Sand Soldier participates in combat with its additional might from the Equipment

Nuances:

• The Sand Soldier must enter play at the same battlefield where Guards! was hidden (the battlefield where combat is occurring)
• If Guards! was hidden at a different battlefield, the Sand Soldier enters play there and does not participate in the current combat
• "Playing" a token (when an ability says "Play a token") counts as playing that unit and triggers "When you play me" abilities like Weaponmaster
• This bypasses the normal restriction that [Equip] abilities can only be activated during your Main Phase in an Open State