Agnerod East Imperial Staff

I recently obtained one of these. I normally use Arc, but that does not really seem to suit the properties of this staff. I would be curious to know what sort of build (particularly as witch) would be designed around this staff?

Perhaps if the 40% lightning pen property would stack with a gem? Spitballing, Lightning Trap might be a possibility. Just based on my own play style - Pledge seems superior.

Might work with Herald of Thunder as main skill, since it's unaffected by Spell Damage or Crit.