When Heimerdinger copies Caitlyn's ability, does Heimerdinger need to be at a battlefield to activate it, or does he only copy the Exhaust part?

Ruling: Heimerdinger copies Caitlyn's entire ability, including both the Exhaust effect and the battlefield location requirement.

Nuances:

• The second text block stating "you must be at a battlefield" is part of the same ability, not a separate condition
• Heimerdinger must meet all requirements of the copied ability, including location restrictions