Recently played The Forgotten Age and I drew this card. On it, it says " You get -1 (Fight), -1 health and gain the Serpent trait." What is the point of the Serpent trait? I looked through the campaign and I could not find where this would come into play. Can someone point it out to me if they know?

I can't seem to find anything either. Maybe it'll matter in Return to the Forgotten Age?

It's strictly for flavor right now. Perhaps new cards in the Return set will make it relevant (though I'd expect them to replace Agents of Yig altogether), or maybe later player cards will tie into having a trait that matches an enemy.

I believe it is more affected by encounter cards, and not so much scenario effects.

It has no effect, as everything that references the Serpent trait specifies a Serpent enemy. However, that's hardly the most egregious wasted element of TFA. I imagine there'll be a number of things that will be addressed in the inevitable Return To The Forgotten Age...