I know a place in arrapago reef but there's only 7 of them and the repop is 16 mins. so during one lightning day it's only possible to get like...24-30 kills (out of 200).
But then there's the Qutrubs outside of Dvucca Isle staging point. There seems to be a good amount, but there's also blood aggro (jnun, skeles), imps, and dark elementals during dark weather.
Anyone have any experience with the particular trial?