Do you need to have a gear in play (on base or battlefield) to use a card that says 'you may kill a gear'?

Ruling: Yes, you need to have at least one gear on board to use this card. The card requires a valid target to enter the chain.

Nuances:

• When the spell resolves, you can choose whether or not to actually destroy the targeted gear
• If the card said "Kill up to one gear" instead, you could play it without having a gear on board