The Lesser Anti Beholder Crystal off the DDO Store does not stop Enervation - Soloing Invaders on Casual difficulty on my lvl 8 FS/4 Fighter I'm taking 6-9 Neg Levels each time {not each time I go in the quest but each set of beholders/elder beholder}.
I have Deathblock of course and I know Deathward is a complete waste of time around Beholders which is why I decided on Casual {knowing I was likely to take negs} but 4 per shot is just ridiculous and the fact that the Crystal off the store does nothing to stop this even more so.