Can Lee Sin activate his abilities or play his signature spell (Dragon's Rage) during Showdown when defending a battlefield?

Ruling: You can only activate abilities during your turn in a neutral open state. Dragon's Rage cannot be played in combat because it does not say action or reaction on it.

Nuances:

• Buffs (specifically the keyword 'buff') are permanent and will persist when you pass turn to your opponent
• Other might increases that are not specifically labeled as 'buff' are not permanent