Can Ezreal Prodigy's energy cost reduction ability be applied to a card with no energy cost (like Called Shot) to enable paying power for optional additional costs like triggering purple Sivir?

Ruling: You can choose to apply Ezreal Prodigy's energy cost reduction ability even when a card has no energy cost. However, this only applies to optional additional costs.

Nuances:

• The reduction works for optional additional costs like Repeat
• There may be limitations on which optional additional costs this applies to