When Heimerdinger is on board with multiple artifacts (Iron Ballista and Energy Conduit), can he activate all of their abilities when he exhausts, or only one?

Ruling: Heimerdinger can only activate one artifact ability when he exhausts, not all of them simultaneously.

Nuances:

• Even though Heimerdinger's text says he has "all" the abilities, he must choose which single ability to use when exhausting
• The abilities are separate lines/effects, not one combined effect