My hunch is it comes from the combination of Opportunist (10 CP passive in Ritual), Crushing Shock spam and not using any physical attacks, thus repeatedly triggering the Opportunist without utilizing it.
The glow effect from Opportunist stacks and persists after death:

And here it is together with Inner Light, Boundless Storm, Hardened Ward and Crystal Fragments proc:
EU ‣ Wabbajack nostalgic ‣ Blackwater Blade defender ‣ Kyne wanderer
The offspring of the root of all evil in ESO by DeanTheCat
Why ESO needs a monthly subscriptionWhen an MMO is designed around a revenue model rather than around fun, it doesn’t have a long-term future. ―
Richard A. BartleTheir idea of transparent, at least when it comes to communication, bears a striking resemblance to a block of coal. ―
lordrichter... in the balance of power between the accountants and marketing types against the artists, developers and those who generally want to build and run a good game then that balance needs to always be in favour of the latter - because the former will drag the game into the ground for every last bean they can squeeze out of it. ―
Santie Claws