Stormbeacon Blade
Artifact — Equipment
Equipped creature gets +3/+0.
Whenever equipped creature attacks, draw a card if you control three or more attacking creatures.
Equip 
(: Attach to target creature you control. Equip only as a sorcery.)
"Sky and Ember, guide my blade!"
Jorge Jacinto
Rulings
The second ability checks the number of attacking creatures you control only as the ability resolves. If another attack trigger (such as from the mobilize ability) puts creatures onto the battlefield attacking, you can choose to order the triggered abilities so that those creatures enter before Stormbeacon Blade’s ability resolves.
(wotc • 2025-04-04)
Rulings
The second ability checks the number of attacking creatures you control only as the ability resolves. If another attack trigger (such as from the mobilize ability) puts creatures onto the battlefield attacking, you can choose to order the triggered abilities so that those creatures enter before Stormbeacon Blade’s ability resolves.
(wotc • 2025-04-04)