Anyway, after some searching I noticed a tree in that area on the right just before you reach the ents. It looked kind of odd, so I gave it a swipe. Guy jumps out of his Chameleon spell and nails me with a lightning sword. I got myself set for a fight, when all of a sudden this dude, wearing that goofy Catarina armor, starts running like a fat kid trying to flee a wedgie. I mean he was really running, not even looking back. Went all the way through to the the slope down to Sif's door. When I caught up, I hit him with a backstab and killed him.
It was like he didn't even know he was supposed to be the one attacking me. One theory is that he had joined the forest hunters for the first time, but had no clue how it worked. Wondered if maybe when he got summoned by the ring, he thought for some reason he was actually being invaded.
Anyway, I wish I could have video captured him running like a madman in that armor.