Spoiler Alert! We have hidden this information so that you have the choice to try it on your own, or have the advantage of knowing how the sausage is made...
Simply click on a Decay Generator. There are 2 close by, on either side of the steps leading up to the Temple. Just kill the Septic Breath Shadows guarding it, then step to the side carefully and click on the Decay Generator.
In all other zones they do not reward XP, TP or Gold, only Public Event Points. In all other aspects they are the same as a Daily Quest (except for the infinitely repeatable part and the rewards). Public Event Points contribute towards the completion of Regional Quest objectives, which in turn rewards a number of Energy of Justice commensurate with your amount of participation in the Regional event.