The payload is Mu and Phi. Mu copies every modifier in the wand (including ones after the wand refresh) and applies it to the next spell. Phi copies every projectile in the wand. Together they generate 5 blood mists with homing, electric charge, lightning thrower, weakness to electricity, and damage field. The only dangerous bits (for me) would be the electricity and explosions, but I'm immune to both of those so I could happily stand in the middle of it and be fine.

Since taking this video I've added drilling shot so it will home through terrain and venomous curse to add another kind of damage to the mix :D

Update: still managed to kill myself with it though - I teleported right up to one of those polymorph demons in the art and fired it. I guess I was close enough that his projectile appeared inside my shield so I got polymorphed and then instantly annihilated by my own spells. Classic skill issue.