Strobelights - everyone can see it
 

See GIF below:

It seems to have to do with lightsources or double light sources - I'm not really sure. Sometimes equipping and unequipping Stein of Moggok helps. But not usually.

This happens quite often - and usually randomly triggers.

https://media.giphy.com/media/JozR70...Ea8u/giphy.gif

If you equip and unequip light sources really fast the game glitches and the strobe effect keeps going until you camp....and possibly zone.

I can confirm this has been in the game for years as I do this when I'm bored to annoy my fellow neckbeards.

Edit: I have tested this with friends and the effect is global not just confined to the client of the annoyer.

Double edit: once the stobe effect triggers its fun to rapidly swap robes and shout "DISCOWIZARD!!!1!"

To add: If you don't equip/unequip at all, it'll still do this. There's a possibility it could trigger from an illusion, now that I'm thinking about it. Dark Elf in the GIF above is my native form, but I was PREVIOUSLY wood elf or whatever.

It's possible that when you switch illusion forms, it acts as if you're equipping/unequipping your light sources really fast, then permanently pulses until you log.