Maintenance for the week of October 5:
• [COMPLETE] ESO Store and Account System for maintenance – October 8, 8:00AM EDT (12:00 UTC) – 12:00PM EDT (16:00 UTC)
This happened to me last week while questing in Veteran Shadowfen. I believe it was as a result of a quest that turned me into a skeleton (I remember having zero health regen). Either way, at first it was only on my screen once and I just ignored it. Since then, it has kinda grown exponentially. I don't notice a pattern, but it seems to be when I die that I gain another one of these buffs. I have not determined if there is an in-game effect, but it makes my character screen impossible to read.
Also, these screens are provided 100% add-on free for your unmolested viewing (dis)pleasure.