OMG, you just reminded me of my first discovery of friendly fire in BG2 where Blade Barrier was concerned! I had forgotten all about it.
Anomen had levelled to the point of getting Blade Barrier, and I had gathered everyone for buffs before walking down to a red drgaon to talk smack.
I got everyone buffed up, Anomen was in the middle of everyone else, I had him cast blade barrier - boom! Everyone ripped to shreds.
For the uninitiated - Blade Barrier surrounds the cleric and moves with him/her. More like a force field type effect.
Once I learned that, though, he became my undead Cuisinart.
And I lost the party to friendly cloudkills probably half a dozen times before I figured out what was killing them. Cloudkills in DDO are extremely weak in comparison.
Lightning Bolt - not for the faint of heart