Does a unit played with Block during a showdown get +3 might from its Shield 3 effect?

Ruling: Yes, the unit gets +3 might from Shield 3 because "While it's a defender" is a constant ability that applies during the showdown, unlike "When I defend" which is a trigger.

Nuances:

• Constant abilities ("While it's a defender") work differently than triggered abilities ("When I defend")
• The constant ability applies even though Shield/Assault are applied before the initial chain