When do you declare the target for an ability - upon resolution or upon entering the battlefield?

Ruling: You declare the target when the ability goes on the chain at the start of combat, not when the unit enters the battlefield or when the ability resolves.

Sequence:

• Unit enters the battlefield
• Combat begins and showdown opens
• All attacker triggers go on the initial chain
• You finalize the chain by declaring targets for abilities at this time
• Abilities resolve with their declared targets