If Ezreal is defending and triggers his on-defend ability, then you play Arcane Shift to replay him to the same battlefield, does he trigger his on-defend ability again?

Ruling: Yes, Ezreal will trigger his on-defend ability again. When Arcane Shift replays Ezreal, it creates a new instance of the unit that gains the defender designation for the first time, triggering the ability.

Sequence:

• Ezreal defends and his on-defend ability triggers and resolves
• Play Arcane Shift, which banishes and replays Ezreal to the same battlefield (dealing 3 damage from Arcane Shift)
• The new Ezreal instance gains defender status for the first time
• Ezreal's on-defend ability triggers again

Nuances:

• Simply moving a unit in and out of combat does not grant a second trigger; Arcane Shift works because it replays the unit as a new instance
• All gear on Ezreal drops to your base when banished, so the second trigger will only deal 3 damage (base power)
• On-attack/on-defend triggers occur when a unit gains the designation for the first time in combat, not just at the beginning of combat
• This interaction only works on defense (not offense) because you can only play units to zones you control
• If you use Ride the Wind to move Ezreal to another battlefield, he would trigger again there, but only after the current showdown ends and only if he's still present when the new showdown begins