If I target one of my two Poros with Discipline, and my opponent uses Gust on the targeted Poro, can I choose the other Poro as a new target?

Ruling: No, you cannot retarget. When the original target becomes invalid, you do not get to choose a new target.

Nuances:

• This applies when a card like Gust removes the targeted unit before the ability resolves
• The ability does not allow retargeting even if other valid targets exist on the battlefield