Charged Grid can be used to damage large mobs that are surrounding the Temple Guardian. It goes well in combination with other AoE spells like Fiery Ember, Icy Evanescence, and/or Deathly Spears. Note that Charged Grid has a high cooldown compared to those spells, so casting them separately may be better than putting them together into a combo.
Mod with both Substance mods and Longetivity to maximize the defensive/healing effect of the spell. The healing effects work on both the Temple Guardian and his allies.
Choose Havoc - Unnatural Selection - Widen for maximum damage and mayhem against enemies.
Range is smaller than Icy Evanescence or Fiery Ember, but it can be improved with +combat art range item modifiers.
Pros and Cons
The grid follows the Temple Guardian around while it lasts