Fulguritis

Fulguritis is an attack type spell that shoots lightning from the tip of the wand. When fully casted on another player, they lose 3 quarters of their health points.

In game description:

"Produces a continuous stream of lightning from your wand. Hold down mouse button to use"

This spell is very popular among Ro Wizard gamers.

Location
Just outside the Great hall: walk toward the outside and go in the left pillar once outside.