These lights come from the top and bottom of the screen and move towards the middle. They're only visible with first person camera and only on this character. It's a redguard templar with some sai sahan style things on, if that matters. I have no buffs whatsoever on what might do this.
Is this a bug or some weird feature that I don't understand?
It reminds me of migraine attacks I had years ago and I'm fearing looking at stuff like this too often might trigger them again.