Unit design traits - where do they come from?
I have a vague notion that the traits that are available when designing a unit vary. Of course Henchmen have access to the magic traits, but I'm sure I've seen other traits come and go. What determines the available traits? Technology, equipment, race? All three? Does the "charge" trait only appear if you have a mount equipped, for example?
I'd actually enjoy specific traits that come from any or all of those, but I've never noticed a pop-up window that informed me "researching this allows this trait" or "equipping this allows this trait".