Deluvian lightning spheres are alchemical electrical grenades used by the Deluvian Empire (and possibly also the Illud). They can safely be thrown into the chaotic melee of battle, as Kua Toa are highly resistant to electrical damage in this setting, even more so than in regular 3.5e.
The physical mechanism is simple; a glass sphere full of one liquid is placed within a metal casing filled with another liquid. When the glass breaks (usually from hurling the sphere upon the ground), the two fluids begin to mix, and after a few seconds, the alchemical reaction produces a dangerous electric pulse.
A number of lighting spheres were used to eliminate the majority of Jimmy's Warbonders in Episode 2, but they have not been seen since.