Do spells/actions trigger 'when defending' effects, or do those effects only apply when units are moved to a battlefield to start a showdown?

Ruling: 'When defending' or 'when I defend' effects are only active during showdowns where that card is the defender. Spells and actions do not trigger these effects.

Nuances:

• These effects specifically require the card to be the defender in a showdown
• Simply being targeted by spells or actions does not activate 'when defending' triggers